* common/filestuff.c: Check USE_WIN32API before including
	sys/socket.h.
	(HAVE_F_GETFD): New define.
	(mark_cloexec): Check HAVE_F_GETFD.
	(gdb_open_cloexec): Change 'mode' to unsigned long.
	(gdb_socketpair_cloexec): Check HAVE_SOCKETPAIR.
	(gdb_pipe_cloexec): Check HAVE_PIPE.
	* common/filestuff.h (gdb_open_cloexec): Change 'mode' to unsigned
	long.