Optimize a < 0 ? -1 : 0 to (signed)a >> 31.

Optimize a < 0 ? -1 : 0 to (signed)a >> 31.

Try to optimize x < 0 ? -1 : 0 into (signed) x >> 31
and x < 0 ? 1 : 0 into (unsigned) x >> 31.

Move the optimization did in ix86_expand_int_vcond to match.pd

gcc/ChangeLog:

	PR target/114189
	* match.pd: Simplify a < 0 ? -1 : 0 to (signed) >> 31 and a <
	0 ? 1 : 0 to (unsigned) a >> 31 for vector integer type.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/avx2-pr115517.c: New test.
	* gcc.target/i386/avx512-pr115517.c: New test.
	* g++.target/i386/avx2-pr115517.C: New test.
	* g++.target/i386/avx512-pr115517.C: New test.
	* g++.dg/tree-ssa/pr88152-1.C: Adjust testcase.