Prepare for gnulib update

After the last gnulib import (Dec 2012), gnulib upstream started
replacing mingw's 'struct timeval' with a version with 64-bit time_t,
for POSIX compliance:

 commit f8e84098084b3b53bc6943a5542af1f607ffd477
 Author: Bruno Haible <bruno@clisp.org>
 Date:   Sat Jan 28 18:12:10 2012 +0100
     sys_time: Override 'struct timeval' on some native Windows platforms.

See:

 https://lists.gnu.org/archive/html/bug-gnulib/2012-01/msg00372.html

However, that results in conflicts with native Winsock2's 'select':

select()'s argument
	http://sourceforge.net/p/mingw-w64/mailman/message/29610438/

... and libiberty's timeval-utils.h timeval_add/timeval_sub, at the
least.

We don't really need the POSIX compliance, so this patch prepares us
to simply not use gnulib's 'struct timeval' replacement once a more
recent gnulib is imported, thus preserving the current behavior, by
adding a sys/time.h wrapper header that undefs gnulib's replacements,
and including that everywhere instead.

The SIZE -> OSIZE change is necessary because newer gnulib's
sys/time.h also includes windows.h/winsock2.h, which defines a
conflicting SIZE symbol.

Cross build-tested mingw-w64 32-bit and 64-bit.
Regtested on x86_64 Fedora 20.

gdb/ChangeLog:
2015-08-24  Pedro Alves  <palves@redhat.com>

	* Makefile.in (HFILES_NO_SRCDIR): Add common/gdb_sys_time.h.
	* common/gdb_sys_time.h: New file.
	* event-loop.c: Include gdb_sys_time.h instead of sys/time.h.
	* gdb_select.h: Likewise.
	* gdb_usleep.c: Likewise.
	* maint.c: Likewise.
	* mi/mi-main.c: Likewise.
	* mi/mi-parse.h: Likewise.
	* remote-fileio.c: Likewise.
	* remote-m32r-sdi.c: Likewise.
	* remote.c: Likewise.
	* ser-base.c: Likewise.
	* ser-pipe.c: Likewise.
	* ser-tcp.c: Likewise.
	* ser-unix.c: Likewise.
	* symfile.c: Likewise.
	* symfile.c: Likewise.  Rename OSIZE to SIZE throughout.
	* target-memory.c: Include gdb_sys_time.h instead of sys/time.h.
	* utils.c: Likewise.

gdb/gdbserver/ChangeLog:
2015-08-24  Pedro Alves  <palves@redhat.com>

	* debug.c: Include gdb_sys_time.h instead of sys/time.h.
	* event-loop.c: Likewise.
	* remote-utils.c: Likewise.
	* tracepoint.c: Likewise.

gdb/utils.c

@@ -62,7 +62,7 @@
 
 #include "readline/readline.h"
 
-#include <sys/time.h>
+#include "gdb_sys_time.h"
 #include <time.h>
 
 #include "gdb_usleep.h"