Do not include config.h directly

Do not include config.h directly

All source files under gdb/ that include headers from gdb/ include
either defs.h or server.h before any other code with the exception
of gdb/gdbserver/gdbreplay.c which seems to be a special case.  Both
defs.h and server.h include both our and gnulib's config.h files as
their first non-comment line, so no other file ever needs to directly
include any config.h.  This commit removes two such direct config.h
includes.

gdb/
2014-07-30  Gary Benson  <gbenson@redhat.com>

	* common/common-utils.h: Do not include config.h.
	* nat/linux-btrace.h: Likewise.