Rename bits/stdio-lock.h to stdio-lock.h (bug 14912).

Rename bits/stdio-lock.h to stdio-lock.h (bug 14912).

It was noted in
<https://sourceware.org/ml/libc-alpha/2012-09/msg00305.html> that the
bits/*.h naming scheme should only be used for installed headers.
This patch renames bits/stdio-lock.h to plain stdio-lock.h to follow
that convention.

Tested for x86_64 (testsuite, and that installed stripped shared
libraries are unchanged by the patch).

	[BZ #14912]
	* bits/stdio-lock.h: Move to ...
	* sysdeps/generic/stdio-lock.h: ...here.
	(_BITS_STDIO_LOCK_H): Rename macro to _STDIO_LOCK_H.
	* sysdeps/nptl/bits/stdio-lock.h: Move to ...
	* sysdeps/nptl/stdio-lock.h: ...here.
	(_BITS_STDIO_LOCK_H): Rename macro to _STDIO_LOCK_H.
	* include/libio.h: Include <stdio-lock.h> instead of
	<bits/stdio-lock.h>.
	* sysdeps/nptl/fork.c: Likewise.
	* sysdeps/pthread/flockfile.c: Likewise.
	* sysdeps/pthread/ftrylockfile.c: Likewise.
	* sysdeps/pthread/funlockfile.c: Likewise.