tree-optimization/112320 - bougs debug IL after SCCP

tree-optimization/112320 - bougs debug IL after SCCP

The following addresses wrong debug IL created by SCCP rewriting stmts
to defined overflow.  I addressed another inefficiency there but
needed to adjust the API of rewrite_to_defined_overflow for this
which is now taking a stmt iterator for in-place operation and a
stmt for sequence producing because gsi_for_stmt doesn't work for
stmts not in the IL.

	PR tree-optimization/112320
	* gimple-fold.h (rewrite_to_defined_overflow): New overload
	for in-place operation.
	* gimple-fold.cc (rewrite_to_defined_overflow): Add stmt
	iterator argument to worker, define separate API for
	in-place and not in-place operation.
	* tree-if-conv.cc (predicate_statements): Simplify.
	* tree-scalar-evolution.cc (final_value_replacement_loop):
	Likewise.
	* tree-ssa-ifcombine.cc (pass_tree_ifcombine::execute): Adjust.
	* tree-ssa-reassoc.cc (update_range_test): Likewise.

	* gcc.dg/pr112320.c: New testcase.