doc/texi2pod: make references bold

Inspired by GCC r86635.

This is more consistent with other man pages. For example in `man git`,
all the "git-help(1)" kind of cross refs are bold.
Signed-off-by: Timothy Gu <timothygu99@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/texi2pod.pl

@@ -377,8 +377,8 @@ sub postprocess
     s/\(?\@xref\{(?:[^\}]*)\}(?:[^.<]|(?:<[^<>]*>))*\.\)?//g;
     s/\s+\(\@pxref\{(?:[^\}]*)\}\)//g;
     s/;\s+\@pxref\{(?:[^\}]*)\}//g;
-    s/\@ref\{(?:[^,\}]*,)(?:[^,\}]*,)([^,\}]*).*\}/$1/g;
-    s/\@ref\{([^\}]*)\}/$1/g;
+    s/\@ref\{(?:[^,\}]*,)(?:[^,\}]*,)([^,\}]*).*\}/B<$1>/g;
+    s/\@ref\{([^\}]*)\}/B<$1>/g;
     s/\@noindent\s*//g;
     s/\@refill//g;
     s/\@gol//g;