Fix gen-auto-libm-tests sticky bit setting for negative results.

gen-auto-libm-tests has a bug in the logic for setting a sticky bit
based on the ternary value from MPFR: it is correct for positive
results, but for negative results mpz_setbit acts as if a two's
complement representation is used, whereas the low bit needs setting
based on the sign-magnitude representation GMP actually uses.  (This
showed up in converting fma tests to use auto-libm-test-in /
gen-auto-libm-tests.)

This patch fixes the problem by negating the mpz_t value to set its
low bit.  There are lots of changes to auto-libm-test-out (mainly 1ulp
fixes to ldbl-128 expected results), but only a few ulps updates are
needed on x86 / x86_64.  In one case, a corrected expectation showed
up a spurious underflow exception where the correct result is slightly
outside the underflowing range.

Tested x86_64 and x86 and ulps updated accordingly.

	* math/gen-auto-libm-tests.c (adjust_real): Ensure integers are
	non-negative before setting low bit.
	* math/auto-libm-test-in: Mark one asin test possibly having
	spurious underflow.
	* math/auto-libm-test-out: Regenerated.
	* sysdeps/i386/fpu/libm-test-ulps: Update.
	* sysdeps/x86_64/fpu/libm-test-ulps: Likewise.