powerpc64: Always restore TOC on longjmp [BZ #21895]

This patch changes longjmp to always restore the TOC pointer (r2 register)
to the caller frame on powerpc64 and powerpc64le.  This is related to bug
21895 that reports a situation where you have a static longjmp to a
shared object file.

	[BZ #21895]
	* sysdeps/powerpc/powerpc64/__longjmp-common.S: Remove condition code for
	restoring r2 in longjmp.
	* sysdeps/powerpc/powerpc64/Makefile: Added tst-setjmp-bug21895-static to
	test list.
	Added rules to build test tst-setjmp-bug21895-static.
	Added module setjmp-bug21895 and rules to build a shared object from it.
	* sysdeps/powerpc/powerpc64/setjmp-bug21895.c: New test file.
	* sysdeps/powerpc/powerpc64/tst-setjmp-bug21895-static.c: New test file.

Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>