Bump required version of texinfo to 4.7

It seems we require texinfo 4.7 for the --plaintext option, so
document that and check for the correct version in configure.

ChangeLog:

2014-12-15  Will Newton  <will.newton@linaro.org>

	* manual/install.texi: Bump required version of texinfo
	to 4.7 from 4.5.
	* INSTALL: Regenerated.
	* configure.ac: Check for makeinfo version 4.7 and above.
	* configure: Regenerated.
CVE-2012-3406: Stack overflow in vfprintf [BZ #16617]

A larger number of format specifiers coudld cause a stack overflow,
potentially allowing to bypass _FORTIFY_SOURCE format string
protection.
Remove custom pthread_once implementation on s390.
stdio-common: Include <libc-internal.h> in some tests

This patch adds the missing libc-internal.h include on test-vprintf.c
tst-sprintf.c.
Fix nptl/tst-mutex5.c: Do not skip tests if elision is enabled.
Fix nptl/tst-sem4: always start with a fresh semaphore.
Add comments for the generic lowlevellock implementation.

Patch by Bernard Ogden <bernie.ogden@linaro.org>.
Return allocated array instead of unallocated.

In locale/programs/ld-ctype.c we returned array that was on stack.
Fixed by returning static array instead.