MFH: r512436

Fix groff build with libc++ 9.0.0

Because libc++ 9.0.0 now includes <math.h> from <stdlib.h>, groff fails
to build with an error similar to:

In file included from src/libs/libgroff/assert.cpp:20:
In file included from /usr/include/c++/v1/stdlib.h💯
./lib/math.h:38:3: error: "Please include config.h first."
 #error "Please include config.h first."
  ^
./lib/math.h:40:1: error: unknown type name '_GL_INLINE_HEADER_BEGIN'
_GL_INLINE_HEADER_BEGIN
^

Fix this in the least intrusive way, by simply including config.h
instead of emitting an error message.

Approved by:	portmgr (joneum)
PR:		240701

textproc/groff/files/patch-lib_math.in.h

@@ -0,0 +1,11 @@
+--- lib/math.in.h.orig	2018-12-23 14:34:15 UTC
++++ lib/math.in.h
+@@ -34,7 +34,7 @@
+ #endif
+ 
+ #ifndef _GL_INLINE_HEADER_BEGIN
+- #error "Please include config.h first."
++# include "config.h"
+ #endif
+ _GL_INLINE_HEADER_BEGIN
+ #ifndef _GL_MATH_INLINE