Fix powerpc32 llround, llroundf exceptions (bug 19125).

Fix powerpc32 llround, llroundf exceptions (bug 19125).

The powerpc32 implementations of llroundf and llround produce spurious
and missing exceptions (some arising from such exceptions from
conversions to long long, some present even when fctidz is used).

This patch fixes those problems in a similar way to the llrint /
llrintf fixes.  The spurious exceptions in the fctidz case for large
arguments arise from a converted value that saturated as LLONG_MAX
being converted back to float or double (the conversion back being
inexact, but "inexact" must not be raised together with "invalid"),
and from the subtraction x - xrf also being inexact for sufficiently
large arguments (whether the saturation was to LLONG_MAX or
LLONG_MIN); those are fixed by returning early if the argument is
large enough that no rounding is needed.

This code is not used for --with-cpu=power4 builds (I suspect the code
used in that case may also produce spurious "inexact" exceptions, but
that's something to investigate later).

Tested for powerpc.

	[BZ #19125]
	* sysdeps/powerpc/powerpc32/fpu/s_llround.c: Include <limits.h>,
	<math_private.h> and <stdint.h>.
	(__llround): Avoid conversions to and from long long int, and
	subtractions, where those might raise spurious exceptions.
	* sysdeps/powerpc/powerpc32/fpu/s_llroundf.c: Include
	<math_private.h> and <stdint.h>.
	(__llroundf): Avoid conversions to and from long long int, and
	subtractions, where those might raise spurious exceptions.