Allow cross-building of tests

Allow building tests in a cross configuration without a test wrapper
defined. This is helpful for doing simple build testing of tests.

ChangeLog:

2014-09-30  Will Newton  <will.newton@linaro.org>

	* localedata/Makefile: Move assignment to tests-special
	into an ifdef testing run-built-tests.
	* timezone/Makefile: Likewise.
stdlib/tst-strtod-round.c: Fix build on ARM

Building this test on ARM fails because the prototypes for the long
double variants of the math functions are unavailable.

Add an additional include guard to math.h that enables long double math
function declarations if _LIBC_TEST is defined and define _LIBC_TEST in
stdlib/tst-strtod-round.c.

ChangeLog:

2014-09-30  Will Newton  <will.newton@linaro.org>

	* math/math.h: Define long double math functions if
	_LIBC_TEST is defined.
	* stdlib/tst-strtod-round.c: Define _LIBC_TEST.
Move some *at definitions to syscalls.list (bug 14138).

Continuing the move of syscall definitions to syscalls.list, where the
removal of support for old kernel versions has made this possible,
this patch moves definitions of various *at functions in
sysdeps/unix/sysv/linux/.

These particular moves are straightforward: there are no #includes of
these source files, no special architecture-specific versions, no
special symbol version handling and no aliases.  Each source file can
be replaced by a single line in sysdeps/unix/sysv/linux/syscalls.list.

Tested for x86_64.

	[BZ #14138]
	* sysdeps/unix/sysv/linux/syscalls.list (fchownat): New syscall.
	(linkat): Likewise.
	(mkdirat): Likewise.
	(readlinkat): Likewise.
	(renameat): Likewise.
	(symlinkat): Likewise.
	(unlinkat): Likewise.
	* sysdeps/unix/sysv/linux/fchownat.c: Remove file.
	* sysdeps/unix/sysv/linux/linkat.c: Likewise.
	* sysdeps/unix/sysv/linux/mkdirat.c: Likewise.
	* sysdeps/unix/sysv/linux/readlinkat.c: Likewise.
	* sysdeps/unix/sysv/linux/renameat.c: Likewise.
	* sysdeps/unix/sysv/linux/symlinkat.c: Likewise.
	* sysdeps/unix/sysv/linux/unlinkat.c: Likewise.