My patch to render mathematical symbols and greek letters intelligibly

in ASCII output finally got committed upstream.  Use it in OpenBSD
right away, such that related work on mandoc can proceed.
Maybe we can even improve libm documentation before release.

textproc/groff/Makefile

@@ -1,10 +1,10 @@
-# $OpenBSD: Makefile,v 1.37 2017/07/26 22:45:30 sthen Exp $
+# $OpenBSD: Makefile,v 1.38 2017/08/22 23:28:52 schwarze Exp $
 
 COMMENT =		GNU troff typesetter
 VERSION =		1.22.3
 SUBST_VARS =		VERSION
 DISTNAME =		groff-${VERSION}
-REVISION =		7
+REVISION =		8
 
 CATEGORIES =		textproc
 DPB_PROPERTIES =	parallel

textproc/groff/patches/patch-tmac_tty-char_tmac

@@ -0,0 +1,268 @@
+$OpenBSD: patch-tmac_tty-char_tmac,v 1.1 2017/08/22 23:28:52 schwarze Exp $
+
+Intelligible ASCII rendering of mathematical symbols and greek letters.
+Accepted and committed upstream.
+
+Index: tmac/tty-char.tmac
+--- tmac/tty-char.tmac.orig
++++ tmac/tty-char.tmac
+@@ -9,7 +9,8 @@
+ .\" - work with all of -Tascii, -Tlatin1, -Tutf8, and -Tcp1047.
+ .\" - work on devices that display only the last overstruck character
+ .\"   as well as on devices that support overstriking
+-.\" - represent the character's graphical shape (not its meaning)
++.\" - help understanding the character's meaning, only aiming to imitate
++.\"   a particular graphical shape when that doesn't hinder understanding
+ .\"
+ .\" Note that the optical appearance of the definitions contained in this
+ .\" file is inferior compared to that of the replacement characters defined
+@@ -30,70 +31,68 @@
+ .tty-char \[rn] \*[tty-rn]
+ .tty-char \[ua] \z|^
+ .tty-char \[da] \z|v
+-.tty-char \[sc] S
++.tty-char \[sc] <section>
+ .tty-char \[ct] \z/c
+-.tty-char \[dg] \z|-
+-.tty-char \[dd] \z|=
+-.tty-char \[ib] (\z=_
+-.tty-char \[ip] \z=_)
+-.tty-char \[sb] (=
+-.tty-char \[sp] =)
+-.tty-char \[if] oo
+-.tty-char \[pt] oc
++.tty-char \[dg] <*>
++.tty-char \[dd] <**>
++.tty-char \[ib] <subset\~or\~equal>
++.tty-char \[ip] <superset\~or\~equal>
++.tty-char \[sb] <proper\~subset>
++.tty-char \[sp] <proper\~superset>
++.tty-char \[if] <infinity>
++.tty-char \[pt] <proportional\~to>
+ .tty-char \[es] {}
+-.tty-char \[ca] (^)
+-.tty-char \[cu] U
+-.tty-char \[de] o
+-.tty-char \[di] -:-
+-.tty-char \[tdi] -:-
++.tty-char \[ca] <intersection>
++.tty-char \[cu] <union>
++.tty-char \[de] <degree>
++.tty-char \[di] /
++.tty-char \[tdi] /
+ .tty-char \[no] ~
+ .tty-char \[tno] ~
+-.tty-char \[gr] \Z'\*[tty-rn]'V
+-.tty-char \[is] \z'\z,I
+-.tty-char \[mo] E
+-.tty-char \[pd] a
+-.tty-char \[sr] \e/
+-.tty-char \[*C] \z_H
+-.tty-char \[*D] \z_/\z_\e
+-.tty-char \[*F] \zIO
+-.tty-char \[*G] |\*[tty-rn]
+-.tty-char \[*H] \z-O
+-.tty-char \[*L] /\e
+-.tty-char \[*P] TT
+-.tty-char \[*Q] \zIY
+-.tty-char \[*S] \z_\Z'\*[tty-rn]'>
+-.tty-char \[*W] \z_O
+-.if c\[ss] .tty-char \[*b] \[ss]
+-.tty-char \[*b] B
+-.tty-char \[*a] a
+-.tty-char \[*c] \z,E
+-.tty-char \[*d] d
+-.tty-char \[*e] e
+-.tty-char \[+e] e
+-.tty-char \[*f] \z|o
+-.tty-char \[+f] \z|o
+-.tty-char \[*g] y
+-.tty-char \[*h] \z-0
+-.tty-char \[+h] \z-0
+-.tty-char \[*i] i
+-.tty-char \[*k] k
+-.tty-char \[*l] \z>\e
+-.tty-char \[*m] \z,u
+-.tty-char \[*n] v
+-.tty-char \[*p] \z-n
+-.tty-char \[+p] \z-w
+-.tty-char \[*q] \z|u
+-.tty-char \[*r] p
+-.tty-char \[*s] \z-o
+-.tty-char \[*t] \z~t
+-.tty-char \[*u] u
+-.tty-char \[*w] w
+-.tty-char \[*x] x
+-.tty-char \[*y] n
+-.tty-char \[*z] \z,C
+-.tty-char \[ts] s
+-.\" Definition of \[ss] should follow that of \[*b].
+-.tty-char \[ss] B
++.tty-char \[gr] <nabla>
++.tty-char \[is] <integral>
++.tty-char \[mo] <element\~of>
++.tty-char \[pd] <del>
++.tty-char \[sr] <sqrt>
++.tty-char \[*C] <Xi>
++.tty-char \[*D] <Delta>
++.tty-char \[*F] <Phi>
++.tty-char \[*G] <Gamma>
++.tty-char \[*H] <Theta>
++.tty-char \[*L] <Lambda>
++.tty-char \[*P] <Pi>
++.tty-char \[*Q] <Psi>
++.tty-char \[*S] <Sigma>
++.tty-char \[*W] <Omega>
++.tty-char \[*b] <beta>
++.tty-char \[*a] <alpha>
++.tty-char \[*c] <xi>
++.tty-char \[*d] <delta>
++.tty-char \[*e] <epsilon>
++.tty-char \[+e] <epsilon>
++.tty-char \[*f] <phi>
++.tty-char \[+f] <phi>
++.tty-char \[*g] <gamma>
++.tty-char \[*h] <theta>
++.tty-char \[+h] <theta>
++.tty-char \[*i] <iota>
++.tty-char \[*k] <kappa>
++.tty-char \[*l] <lambda>
++.tty-char \[*m] <mu>
++.tty-char \[*n] <nu>
++.tty-char \[*p] <pi>
++.tty-char \[+p] <pi>
++.tty-char \[*q] <psi>
++.tty-char \[*r] <rho>
++.tty-char \[*s] <sigma>
++.tty-char \[*t] <tau>
++.tty-char \[*u] <upsilon>
++.tty-char \[*w] <omega>
++.tty-char \[*x] <chi>
++.tty-char \[*y] <eta>
++.tty-char \[*z] <zeta>
++.tty-char \[ts] <sigma>
++.tty-char \[ss] ss
+ .tty-char \[c*] \zO\[mu]
+ .tty-char \[c+] \zO+
+ .tty-char \[AN] ^
+@@ -103,31 +102,31 @@
+ .if c\[md] .tty-char \[pc] \[md]
+ .if c\[pc] .tty-char \[md] \[pc]
+ .if c\[pc] .tty-char \[a.] \[pc]
+-.tty-char \[Im] I
+-.tty-char \[Re] R
++.tty-char \[Im] <Im>
++.tty-char \[Re] <Re>
+ .tty-char \[/L] \z/L
+ .tty-char \[/l] \z/l
+-.tty-char \[%0] %o
++.tty-char \[%0] <permille>
+ .tty-char \[ao] o
+ .tty-char \[a"] """"
+ .tty-char \[ab] \z'`
+ .tty-char \[ah] v
+ .tty-char \[ho] \[ac]
+-.tty-char \[/_] \z_/
++.tty-char \[/_] <angle>
+ .tty-char \[=~] =~
+ .tty-char \[|=] -~
+-.tty-char \[Ah] N
+-.tty-char \[CR] _|
+-.tty-char \[fa] \z-V
+-.tty-char \[nm] \z/E
+-.tty-char \[pp] \z_|
++.tty-char \[Ah] <Aleph>
++.tty-char \[CR] <cr>
++.tty-char \[fa] <for\~all>
++.tty-char \[nm] <not\~element\~of>
++.tty-char \[pp] <perpendicular>
+ .tty-char \[sd] ''
+-.tty-char \[st] -)
+-.tty-char \[te] 3
++.tty-char \[st] <such\~that>
++.tty-char \[te] <there\~exists>
+ .if c\[md] .tty-char \[tf] .\[md].
+-.tty-char \[tf] .:.
++.tty-char \[tf] <therefore>
+ .if c\[md] .tty-char \[3d] .\[md].
+-.tty-char \[3d] .:.
++.tty-char \[3d] <therefore>
+ .tty-char \[wp] p
+ .tty-char \[~~] ~~
+ .tty-char \[Fn] \z,f
+@@ -144,7 +143,7 @@
+ .tty-char \[lt] ,-
+ .tty-char \[rt] -.
+ .\" Latin characters
+-.tty-char \[r!] \z,i
++.tty-char \[r!] !
+ .tty-char \[Po] \z-L
+ .tty-char \[Cs] \zox
+ .tty-char \[Ye] \z=Y
+@@ -153,16 +152,16 @@
+ .tty-char \[Of] \z_a
+ .tty-char \[Fo] <<
+ .tty-char \[a-] \*[tty-rn]
+-.tty-char \[S2] 2
+-.tty-char \[S3] 3
+-.tty-char \[ps] 9|
++.tty-char \[S2] ^2
++.tty-char \[S3] ^3
++.tty-char \[ps] <paragraph>
+ .tty-char \[md] .
+ .tty-char \[pc] .
+ .tty-char \[ac] ,
+-.tty-char \[S1] 1
++.tty-char \[S1] ^1
+ .tty-char \[Om] \z_o
+ .tty-char \[Fc] >>
+-.tty-char \[r?] \z'c
++.tty-char \[r?] ?
+ .tty-char \[`A] \z`A
+ .tty-char \['A] \z'A
+ .tty-char \[^A] \z^A
+@@ -179,7 +178,7 @@
+ .tty-char \['I] \z'I
+ .tty-char \[^I] \z^I
+ .tty-char \[:I] \z"I
+-.tty-char \[-D] \z-D
++.tty-char \[-D] Dh
+ .tty-char \[~N] \z~N
+ .tty-char \[`O] \z`O
+ .tty-char \['O] \z'O
+@@ -192,7 +191,7 @@
+ .tty-char \[^U] \z^U
+ .tty-char \[:U] \z"U
+ .tty-char \['Y] \z'Y
+-.tty-char \[TP] \zIb
++.tty-char \[TP] Th
+ .tty-char \[`a] \z`a
+ .tty-char \['a] \z'a
+ .tty-char \[^a] \z^a
+@@ -209,7 +208,7 @@
+ .tty-char \['i] \z'i
+ .tty-char \[^i] \z^i
+ .tty-char \[:i] \z"i
+-.tty-char \[Sd] \z`\z'o
++.tty-char \[Sd] dh
+ .tty-char \[~n] \z~n
+ .tty-char \[`o] \z`o
+ .tty-char \['o] \z'o
+@@ -222,7 +221,7 @@
+ .tty-char \[^u] \z^u
+ .tty-char \[:u] \z"u
+ .tty-char \['y] \z'y
+-.tty-char \[Tp] \zpb
++.tty-char \[Tp] th
+ .tty-char \[:y] \z"y
+ .\" for Turkish
+ .tty-char "\[G ab]" G
+@@ -230,7 +229,7 @@
+ .tty-char "\[I .]" I
+ .\"tty-char \[:y] \ij
+ .tty-char \[arrowvertex] |
+-.tty-char \[mc] \z,u
++.tty-char \[mc] <micro>
+ .cp \n[_C]
+ .
+ .ie '\*(.T'cp1047' \