GDB i386 ports are now all cleaned up

[Jim Blandy]

Well, at least their register maps are cleaned up, anyway.

Chris Faylor just finished updating the Cygwin port, so now all the
x86 ports of GDB that are in active use rely on a single common base
for their register definitions, provided by tm-i386.h.  This makes it
a bit easier to write code which benefits all the x86 ports.  Check
out http://sourceware.cygnus.com/gdb/papers/linux/i386-includes.png
to see the current state of affairs.

Thanks to everyone for helping clean up the mess!