tree-optimization/107833 - invariant motion of uninit uses

tree-optimization/107833 - invariant motion of uninit uses

The following fixes a wrong-code bug caused by loop invariant motion
hoisting an expression using an uninitialized value outside of its
controlling condition causing IVOPTs to use that to rewrite a defined
value.  PR107839 is a similar case involving a bogus uninit diagnostic.

	PR tree-optimization/107833
	PR tree-optimization/107839
	* cfghooks.cc: Include tree.h.
	* tree-ssa-loop-im.cc (movement_possibility): Wrap and
	make stmts using any ssa_name_maybe_undef_p operand
	to preserve execution.
	(loop_invariant_motion_in_fun): Call mark_ssa_maybe_undefs
	to init maybe-undefined status.
	* tree-ssa-loop-ivopts.cc (ssa_name_maybe_undef_p,
	ssa_name_set_maybe_undef, ssa_name_any_use_dominates_bb_p,
	mark_ssa_maybe_undefs): Move ...
	* tree-ssa.cc: ... here.
	* tree-ssa.h (ssa_name_any_use_dominates_bb_p,
	mark_ssa_maybe_undefs): Declare.
	(ssa_name_maybe_undef_p, ssa_name_set_maybe_undef): Define.

	* gcc.dg/torture/pr107833.c: New testcase.
	* gcc.dg/uninit-pr107839.c: Likewise.