[RFA] Fully disentangle gdb and gdbserver

[Daniel Jacobowitz <drow@mvista.com>]

We were already moving in the direction of separating GDB and gdbserver's
build processes, so I finished the job.  This patch adds a simplified
"terminal.h" to gdbserver, and a configure.srv which substitutes for the
makefile fragments in config/.  After this patch, gdbserver is completely
self-contained, with the exception of the regformats/ directory.

I think this is the right way to go.  I've no objection to adding further
common code later, as long as we have clearly fixed and documented
interfaces between that common code and gdb/gdbserver.


[Forthcoming from me tonight after this patch, probably:
  - host vs. target signal numbering
  - ptrace (PTRACE_GET*REGS) support, which will bring in
    x86-64, i386 floating-point registers, and S-390 ports
    of gdbserver, bringing us back to all the potentially working
    targets from before I started.
  - Warning cleanup, and then turning on warnings in the gdbserver
    directory.
 These along with my pending MI testsuite patch actually make gdbserver
 start to look good...]

OK to commit this?

-- 
Daniel Jacobowitz                           Carnegie Mellon University
MontaVista Software                         Debian GNU/Linux Developer