Revised bugs/ and mailing-lists/ pages

[Andrew Cagney]

FYI,

I (again) revised the http://sources.redhat.com/gdb/bugs/ and 
http://sources.redhat.com/gdb/mailing-lists/ pages.

The one thing interesting (and probably contraversial) is the comment in 
the bugs page on the ``Priority'' entry.  It mentions that ``high'' 
priority is reserved but not why ...   I've stolen the idea from GCC. 
If the GDB group ever decide to track must-fix problems then this 
mechanism is available :-)

Comments fixes typos and rewrites all welcome.

Andrew