PHIOPT: Add support for diamond shaped bb to match_simplify_replacement

PHIOPT: Add support for diamond shaped bb to match_simplify_replacement

This adds diamond shaped form of basic blocks to match_simplify_replacement.
This is the patch is the start of removing/moving all
of what minmax_replacement does to match.pd to reduce the code duplication.

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

Note phi-opt-{23,24}.c testcase had an incorrect xfail as there should
have been 2 if still because f4/f5 would not be transformed as -ABS is
not allowable during early phi-opt.

gcc/ChangeLog:

	* tree-ssa-phiopt.cc (match_simplify_replacement): Add new arguments
	and support diamond shaped basic block form.
	(tree_ssa_phiopt_worker): Update call to match_simplify_replacement

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/phi-opt-23.c: Update testcase.
	* gcc.dg/tree-ssa/phi-opt-24.c: Likewise.