Delete gdb-mi.el

[Eli Zaretskii]

> Date: Fri, 25 Sep 2009 11:13:00 +1200
> From: nickrob@snap.net.nz (Nick Roberts)
> 
> CVS Emacs now uses GDB/MI directly so this file is no longer
> relevant and I would to remove it.

People who use CVS Emacs do not necessarily use CVS GDB, and vice
versa.