Do not raise "inexact" from generic round (bug 15479).

Do not raise "inexact" from generic round (bug 15479).

C99 and C11 allow but do not require ceil, floor, round and trunc to
raise the "inexact" exception for noninteger arguments.  TS 18661-1
requires that this exception not be raised by these functions.  This
aligns them with general IEEE semantics, where "inexact" is only
raised if the final step of rounding the infinite-precision result to
the result type is inexact; for these functions, the
infinite-precision integer result is always representable in the
result type, so "inexact" should never be raised.

The generic implementations of ceil, floor and round functions contain
code to force "inexact" to be raised.  This patch removes it for round
functions to align them with TS 18661-1 in this regard.  The tests
*are* updated by this patch; there are fewer architecture-specific
versions than for ceil and floor, and I fixed the powerpc ones some
time ago.  If any others still have the issue, as shown by tests for
round failing with spurious exceptions, they can be fixed separately
by architecture maintainers or others.

Tested for x86_64, x86 and mips64.

	[BZ #15479]
	* sysdeps/ieee754/dbl-64/s_round.c (huge): Remove variable.
	(__round): Do not force "inexact" exception.
	* sysdeps/ieee754/dbl-64/wordsize-64/s_round.c (huge): Remove
	variable.
	(__round): Do not force "inexact" exception.
	* sysdeps/ieee754/flt-32/s_roundf.c (huge): Remove variable.
	(__roundf): Do not force "inexact" exception.
	* sysdeps/ieee754/ldbl-128/s_roundl.c (huge): Remove variable.
	(__roundl): Do not force "inexact" exception.
	* sysdeps/ieee754/ldbl-96/s_roundl.c (huge): Remove variable.
	(__roundl): Do not force "inexact" exception.
	* math/libm-test.inc (round_test_data): Do not allow spurious
	"inexact" exceptions.