be consistent with man page suffixes

[Jeremy C. Reed]

I see libXi was patched for
https://bugs.freedesktop.org/show_bug.cgi?id=7855

It appears it was decided that the suffix "should be 3 for everyone". For 
example:

  .SH "SEE ALSO"
 -XGrabDevice(3X11)
 +XGrabDevice(3)

But we still have the __LIB_MAN_SUFFIX__ that can be customized (and if I 
read it right, it is "3x" for Linux and Debian's BSD).

This should be done consistent. Either always use one section name or 
always use the macro.

Is there another bug report about this?

On a related note, see https://bugs.freedesktop.org/show_bug.cgi?id=6600

Any comments? (Or explanation?)

Thanks,

  Jeremy C. Reed