MATCH: Add patterns from phiopt's minmax_replacement

This adds a few patterns from phiopt's minmax_replacement
for (A CMP B) ? MIN/MAX<A, C> : MIN/MAX <B, C> .
It is progress to remove minmax_replacement from phiopt.
There are still some more cases dealing with constants on the
edges (0/INT_MAX) to handle in match.

OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

gcc/ChangeLog:

	* match.pd: Add patterns for
	"(A CMP B) ? MIN/MAX<A, C> : MIN/MAX <B, C>".

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/minmax-16.c: Update testcase slightly.
	* gcc.dg/tree-ssa/split-path-1.c: Also disable tree-loop-if-convert
	as that now does the combining.