Optimize A < B ? A : B to MIN_EXPR.

Similar for A < B ? B : A to MAX_EXPR.
There're codes in the frontend to optimize such pattern but failed to
handle testcase in the PR since it's exposed at gimple level when
folding backend builtins.

pr95906 now can be optimized to MAX_EXPR as it's commented in the
testcase.

// FIXME: this should further optimize to a MAX_EXPR
 typedef signed char v16i8 __attribute__((vector_size(16)));
 v16i8 f(v16i8 a, v16i8 b)

gcc/ChangeLog:

	PR target/104401
	* match.pd (VEC_COND_EXPR: A < B ? A : B -> MIN_EXPR): New patten match.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr104401.c: New test.
	* gcc.dg/tree-ssa/pr95906.c: Adjust testcase.