patch 8.1.0419: Cygwin: running cproto fails with -O2

Problem:    Cygwin: running cproto fails with -O2.
Solution:   Strip -O2 for cproto. (Ken Takata, closes #3465)

src/Makefile

@@ -2028,8 +2028,9 @@ proto: $(PRO_AUTO) $(PRO_MANUAL)
 # them as a list of individual flags.
 # The -E"gcc -E" argument must be separate to avoid problems with shell
 # quoting.
+# Strip -O2, it may cause cproto to write stderr to the file "2".
 CPROTO = cproto $(PROTO_FLAGS) -DPROTO \
-	 `echo '$(LINT_CFLAGS)' | sed -e 's/ -[a-z-]\+//g'`
+	 `echo '$(LINT_CFLAGS)' | sed -e 's/ -[a-z-]\+//g' -e 's/ -O[^ ]\+//g'`
 
 ### Would be nice if this would work for "normal" make.
 ### Currently it only works for (Free)BSD make.

src/version.c

@@ -794,6 +794,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    419,
 /**/
     418,
 /**/