Add iseqsig.

Add iseqsig.

TS 18661-1 adds an iseqsig type-generic comparison macro to <math.h>.
This macro is like the == operator except that unordered operands
result in the "invalid" exception and errno being set to EDOM.

This patch implements this macro for glibc.  Given the need to set
errno, this is implemented with out-of-line functions __iseqsigf,
__iseqsig and __iseqsigl (of which the last only exists at all if long
double is ABI-distinct from double, so no function aliases or compat
support are needed).  The present patch ignores excess precision
issues; I intend to deal with those in a followup patch.  (Like
comparison operators, type-generic comparison macros should *not*
convert operands to their semantic types but should preserve excess
range and precision, meaning that for some argument types and values
of FLT_EVAL_METHOD, an underlying function should be called for a
wider type than that of the arguments.)

The underlying functions are implemented with the type-generic
template machinery.  Comparing x <= y && x >= y is sufficient in ISO C
to achieve an equality comparison with "invalid" raised for unordered
operands (and the results of those two comparisons can also be used to
tell whether errno needs to be set).  However, some architectures have
GCC bugs meaning that unordered comparison instructions are used
instead of ordered ones.  Thus, a mechanism is provided for
architectures to use an explicit call to feraiseexcept to raise
exceptions if required.  If your architecture has such a bug you
should add a fix-fp-int-compare-invalid.h header for it, with a
comment pointing to the relevant GCC bug report; if such a GCC bug is
fixed, that header's contents should have a __GNUC_PREREQ conditional
added so that the workaround can eventually be removed for that
architecture.

Tested for x86_64, x86, mips64, arm and powerpc.

	* math/math.h [__GLIBC_USE (IEC_60559_BFP_EXT)] (iseqsig): New
	macro.
	* math/bits/mathcalls.h [__GLIBC_USE (IEC_60559_BFP_EXT)]
	(__iseqsig): New declaration.
	* math/s_iseqsig_template.c: New file.
	* math/Versions (__iseqsigf): New libm symbol at version
	GLIBC_2.25.
	(__iseqsig): Likewise.
	(__iseqsigl): Likewise.
	* math/libm-test.inc (iseqsig_test_data): New array.
	(iseqsig_test): New function.
	(main): Call iseqsig_test.
	* math/Makefile (gen-libm-calls): Add s_iseqsigF.
	* manual/arith.texi (FP Comparison Functions): Document iseqsig.
	* manual/libm-err-tab.pl: Update comment on interfaces without
	ulps tabulated.
	* sysdeps/generic/fix-fp-int-compare-invalid.h: New file.
	* sysdeps/powerpc/fpu/fix-fp-int-compare-invalid.h: Likewise.
	* sysdeps/x86/fpu/fix-fp-int-compare-invalid.h: Likewise.
	* sysdeps/nacl/libm.abilist: Update.
	* sysdeps/unix/sysv/linux/aarch64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/alpha/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/arm/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/hppa/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/i386/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/ia64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/m68k/coldfire/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/m68k/m680x0/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/microblaze/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/mips/mips32/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/mips/mips64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/nios2/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libm.abilist:
	Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libm.abilist:
	Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/libm-le.abilist:
	Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/libm.abilist:
	Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-32/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/sh/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc32/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/libm.abilist:
	Likewise.
	* sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libm.abilist:
	Likewise.
	* sysdeps/unix/sysv/linux/tile/tilepro/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/x32/libm.abilist: Likewise.