Add hints regarding colors etc used by default in recent GDB releases

so that we can just answer "check the readme" when asked about it. :)

devel/gdb/Makefile

@@ -5,6 +5,7 @@ COMMENT=	GNU debugger
 CATEGORIES=	devel
 
 DISTNAME=	gdb-17.1
+REVISION=	0
 
 HOMEPAGE=	https://www.gnu.org/software/gdb/
 

devel/gdb/pkg/PLIST

@@ -13,6 +13,7 @@ include/gdb/jit-reader.h
 @man man/man1/egdb.1
 @man man/man1/egdbserver.1
 @man man/man5/egdbinit.5
+share/doc/pkg-readmes/${PKGSTEM}
 share/gdb/python/
 share/gdb/python/gdb/
 share/gdb/python/gdb/FrameDecorator.py

devel/gdb/pkg/README

@@ -0,0 +1,15 @@
++-------------------------------------------------------------------------------
+| Running ${PKGSTEM} on OpenBSD
++-------------------------------------------------------------------------------
+
+Colors and emoji characters
+===========================
+
+A common question with recent GDB releases is how to disable the use of
+colors and emoji.  To disable both, set
+
+  set style enabled off
+
+in your ~/.gdbinit or export NO_COLOR=1 in your environment (may also
+affect other software).  See "Output Styling" in the info file for
+more fine-grained settings.