[PATCH 2/2] gdbserver: use the new gdb warning helpers

[Doug Evans]

Mike Frysinger writes:
  > We need to use -Wno-missing-prototypes for now as much of the code
  > sticks externs in local files and not in common headers.
  >
  > 2016-01-11  Mike Frysinger  <vapier@gentoo.org>
  >
  > 	* acinclude.m4: Include new ../warning.m4 file.
  > 	* configure: Regenerated.
  > 	* configure.ac: Replace all warning logic with AM_GDB_WARNINGS.

Hi.
LGTM.

[seems obvious enough of a cleanup, but maybe I'm missing something]