* printcmd.c (printf_command): Make format string checking

	* printcmd.c (printf_command): Make format string checking
	stricter.  Add separate cases for long_arg, ptr_arg, and
	long_double_arg.
	* utils.c (xstrvprintf): Improve the error message issued
	for a bad format string.
	* Makefile.in (GDB_WARN_CFLAGS_NO_FORMAT, INTERNAL_CFLAGS_BASE):
	New variables.
	(gnu-v3-abi.o, monitor.o, procfs.o, linux-thread-db.o): Remove
	$(NO_WERROR_CFLAGS).
	(printcmd.o): Likewise.  Use $(GDB_WARN_CFLAGS_NO_FORMAT) and
	enable -Werror.