Add inferred ranges for range-ops based statements.

Add inferred ranges for range-ops based statements.

Gimple_range_fold contains some shorthand fold_range routines for
easy user consumption of that range-ops interface, but there is no equivalent
routines for op1_range and op2_range.  This patch provides basic versions.

Any range-op entry which has an op1_range or op2_range implemented can
potentially also provide inferred ranges.  This is a step towards
PR 113879.  Default is currently OFF for performance reasons as it
dramtically increases the number of inferred ranges.

	PR tree-optimization/113879
	* gimple-range-fold.cc (op1_range): New.
	(op2_range): New.
	* gimple-range-fold.h (op1_range): New prototypes.
	(op2_range): New prototypes.
	* gimple-range-infer.cc (gimple_infer_range::add_range): Do not
	add an inferred range if it is VARYING.
	(gimple_infer_range::gimple_infer_range): Add inferred ranges
	for any range-op statements if requested.
	* gimple-range-infer.h (gimple_infer_range): Add parameter.