[PATCH, rs6000] pr58684, pr83759 xfail test cases that fail on powerpc64.

[PATCH, rs6000] pr58684, pr83759 xfail test cases that fail on powerpc64.

This patch xfails a few test cases on powerpc64 that fail after r256380
due to a longstanding issue with floating-point compares.

See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58684 for more information.

2018-01-30  Bill Seurer  <seurer@linux.vnet.ibm.com>

	PR 58684
	* gcc/testsuite/gcc.dg/torture/inf-compare-1.c: Add xfail.
	* gcc/testsuite/gcc.dg/torture/inf-compare-2.c: Add xfail.
	* gcc/testsuite/gcc.dg/torture/inf-compare-3.c: Add xfail.
	* gcc/testsuite/gcc.dg/torture/inf-compare-4.c: Add xfail.

From-SVN: r257190