soft-fp: Adjust call to abort for kernel use.

soft-fp: Adjust call to abort for kernel use.

soft-fp calls abort in various cases that the code doesn't handle, all
cases that should never actually occur for any supported choice of
types.

Calling an abort function is not appropriate for kernel use, so the
Linux kernel redefines abort as a macro in various ways in the ports
using this code, typically to "return 0" or similar.

One use of abort in soft-fp is inside a comma expression and doesn't
work with such a macro.  This patch changes it to use a statement
expression.

Tested for powerpc-nofpu that installed shared libraries are unchanged
by this patch.

(There are two classes of aborts: those to make control flow visible
to the compiler, in default cases of switches over _FP_CLS_COMBINE,
which could reasonably change to __builtin_unreachable for glibc but
would still need to handle pre-4.5 compilers for kernel use, and those
intended to detect any use of soft-fp for combinations of types the
code doesn't know how to handle, which could reasonably become link
failures if the calls should always be optimized away.  But those are
separate possible future enhancements.)

	* soft-fp/op-common.h (_FP_FROM_INT): Wrap call to abort in
	expression inside statement expression.