Prevent use of uninitialized file lock

Prevent use of uninitialized file lock

The CHECK_INIT() is necessary before the _newlib_flockfile_start() since
this would use otherwise acquire an uninitialized lock which gets
initialized after this leading to a corrupt release.

newlib/ChangeLog
2015-07-01  Sebastian Huber  <sebastian.huber@embedded-brains.de>

	libc/stdio/fputs.c (_puts_r): Add missing CHECK_INIT().
	libc/stdio/gets.c (_gets_r): Add missing _REENT_SMALL_CHECK_INIT() and
	CHECK_INIT().  Use _stdin_r() to get the file pointer instead of stdin.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>