dwarf2out.c: Pass one cv_quals argument instead of two for const and volatile.

dwarf2out.c: Pass one cv_quals argument instead of two for const and volatile.

modified_type_die and add_type_attribute take two separate arguments
for whether the type should be const and/or volatile. To help add
more type modifiers pass the requested modifiers as one cv_quals argument
to these functions. And introduce helper function decl_quals to extract
additional cv_quals from declaration trees.

DWARFv3 added restrict_type [PR debug/59051] and DWARFv5 has proposals
for atomic_type and aligned_type. Which will be easier to implement based
on this change.

gcc/ChangeLog

	* dwarf2out.c (decl_quals): New function.
	(modified_type_die): Take one cv_quals argument instead of two,
	one for const and one for volatile.
	(add_type_attribute): Likewise.
	(generic_parameter_die): Call add_type_attribute with one modifier
	argument.
	(base_type_for_mode): Likewise.
	(add_bounds_info): Likewise.
	(add_subscript_info): Likewise.
	(gen_array_type_die): Likewise.
	(gen_descr_array_type_die): Likewise.
	(gen_entry_point_die): Likewise.
	(gen_enumeration_type_die): Likewise.
	(gen_formal_parameter_die): Likewise.
	(gen_subprogram_die): Likewise.
	(gen_variable_die): Likewise.
	(gen_const_die): Likewise.
	(gen_field_die): Likewise.
	(gen_pointer_type_die): Likewise.
	(gen_reference_type_die): Likewise.
	(gen_ptr_to_mbr_type_die): Likewise.
	(gen_inheritance_die): Likewise.
	(gen_subroutine_type_die): Likewise.
	(gen_typedef_die): Likewise.
	(force_type_die): Likewise.

From-SVN: r214140