combine.c (set_nonzero_bits_and_sign_copies): Use unsigned arithmetics in masking operations.

	* combine.c (set_nonzero_bits_and_sign_copies): Use unsigned
	arithmetics in masking operations.
	(contains_muldiv): Likewise.
	(try_combine): Likewise.
	(find_split_point): Likewise.
	(combine_simplify_rtx): Likewise.
	(simplify_if_then_else): Likewise.
	(simplify_set): Likewise.
	(expand_compound_operation): Likewise.
	(expand_field_assignment): Likewise.
	(make_extraction): Likewise.
	(extract_left_shift): Likewise.
	(make_compound_operation): Likewise.
	(force_to_mode): Likewise.
	(make_field_assignment): Likewise.
	(reg_nonzero_bits_for_combine): Likewise.
	(simplify_shift_const_1): Likewise.
	(simplify_comparison): Likewise.

From-SVN: r166027