Fix powerpc32 lround, lroundf spurious exceptions (bug 19134).

The powerpc32 implementation of lround and lroundf can produce
spurious exceptions from adding 0.5 then converting to integer.  This
includes "inexact" from the conversion to integer (not allowed for
integer arguments to these functions), and, for larger integer
arguments, "inexact", and "overflow" when rounding upward, from the
addition.  In addition, "inexact" is not allowed together with
"invalid" and so inexact addition must be avoided when the integer
will be out of range of 32-bit long, whether or not the argument is an
integer.

This patch fixes these problems.  As in the powerpc64 llround
implementation, a check is added for too-large arguments; in the
powerpc64 case that means arguments at least 2^52 in magnitude (so
that 0.5 cannot be added exactly), while in this case it means
arguments for which the result would overflow "long".  In those cases
a suitable overflowing value is used for the integer conversion
without adding 0.5, while for smaller arguments it's tested whether
the argument is an integer (by adding and subtracting 2^52 to the
absolute value and comparing with the original absolute value) to
avoid adding 0.5 to integers and generating spurious "inexact".

This code is not used when the power5+ sysdeps directories are used,
as there's a separate power5+ version of these functions..

Tested for powerpc.  This gets test-float (for a default powerpc32
hard-float build without any --with-cpu) back to the point where it
should pass once powerpc ulps are regenerated; test-double still needs
another problem with exceptions fixed to get back to that point (and I
haven't looked lately at what default powerpc64 results are like).

	[BZ #19134]
	* sysdeps/powerpc/powerpc32/fpu/s_lround.S (.LC1): New object.
	(.LC2): Likewise.
	(.LC3): Likewise.
	(__lround): Do not add 0.5 to integer or out-of-range arguments.

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