soft-fp: Define and use _FP_STATIC_ASSERT.

soft-fp: Define and use _FP_STATIC_ASSERT.

This patch makes soft-fp use static assertions in place of conditional
calls to abort, in places where there are checks for conditions (on
the types for which a macro is used) that the code is not prepared to
handle.  The fallback definition of _FP_STATIC_ASSERT (for kernel use
only, as only relevant to compilers not supported for building glibc)
is as in misc/sys/cdefs.h.

This means that soft-fp only ever calls abort for _FP_UNREACHABLE
calls in builds with GCC versions before 4.5.  Thus, there is no need
for an abort declaration or <stdlib.h> include, since the kernel code
handles defining abort as a macro itself - and so this avoids any need
for an __KERNEL__ condition on the abort declaration to avoid it
breaking with the kernel's macro definition.  That is, this patch is
intended to make glibc's soft-fp code suitable for kernel use with no
kernel-local changes to the soft-fp code needed at all.

Tested for powerpc-nofpu that installed stripped shared libraries are
unchanged by the patch.  One explicit <stdlib.h> include had to be
added to a file that was relying on the include from soft-fp.h.

	* soft-fp/soft-fp.h (_FP_STATIC_ASSERT): New macro.
	[_LIBC]: Do not include <stdlib.h>.
	[!_LIBC] (abort): Remove declaration.
	* soft-fp/op-2.h (_FP_MUL_MEAT_2_120_240_double): Use
	_FP_STATIC_ASSERT instead of conditionally calling abort.
	* soft-fp/op-common.h (_FP_FROM_INT): Likewise.
	(_FP_EXTEND_CNAN): Likewise.
	(FP_TRUNC): Likewise.
	(__FP_CLZ): Likewise.
	* sysdeps/powerpc/nofpu/flt-rounds.c: Include <stdlib.h>.