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

Do not raise "inexact" from generic floor (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 floor
functions to align them with TS 18661-1 in this regard.  Note that
some architecture-specific versions may still raise "inexact", so the
tests are not updated and the bug is not yet fixed.

Tested for x86_64, x86 and mips64.

	[BZ #15479]
	* sysdeps/ieee754/dbl-64/s_floor.c: Do not mention "inexact"
	exception in comment.
	(huge): Remove variable.
	(__floor): Do not force "inexact" exception.
	* sysdeps/ieee754/dbl-64/wordsize-64/s_floor.c: Do not mention
	"inexact" exception in comment.
	(huge): Remove variable.
	(__floor): Do not force "inexact" exception.
	* sysdeps/ieee754/flt-32/s_floorf.c: Do not mention "inexact"
	exception in comment.
	(huge): Remove variable.
	(__floorf): Do not force "inexact" exception.
	* sysdeps/ieee754/ldbl-128/s_floorl.c: Do not mention "inexact"
	exception in comment.
	(huge): Remove variable.
	(__floorl): Do not force "inexact" exception.