PR c++/12266

	PR c++/12266
	* cp-name-parser.y (struct demangle_info): Remove unused
	member PREV.
	(d_grab): Likewise.
	(allocate_info): Change return type to struct demangle_info *.
	Always allocate a new demangle_info.
	Remove unused PREV pointer.
	(cp_new_demangle_parse_info): New function.
	(cp_demangled_name_parse_free): New function.
	(do_demangled_name_parse_free_cleanup): New function.
	(make_cleanup_cp_demangled_name_parse_free): New function.
	(cp_demangled_name_to_comp): Change return type to
	struct demangle_parse_info *.
	Allocate a new storage for each call.
	(main): Update usage for cp_demangled_name_to_comp
	API change.
	* cp-support.h (struct demangle_parse_info): New structure.
	(cp_demangled_name_to_comp): Update API change for
	return type.
	(cp_new_demangle_parse_info): Declare.
	(make_cleanup_cp_demangled_name_parse_free): New declaration.
	(cp_demangled_name_parse_free): Declare.
	* cp-support.c (cp_canonicalize_string): Update API
	change for cp_demangled_name_to_comp.
	(mangled_name_to_comp): Likewise.
	Return struct demangle_parse_info, too.
	(cp_class_name_from_physname): Update mangled_name_to_comp
	API change.
	(method_name_from_physname): Likewise.
	(cp_func_name): Update API change for cp_demangled_name_to_comp.
	(cp_remove_params): Likewise.
	* python/py-type.c (typy_legacy_template_argument): Likewise.

	* cp-support.h (cp_canonicalize_string_no_typedefs): Declare.
	(cp_merge_demangle_parse_infos): Declare.
	* cp-support.c (ignore_typedefs): New file global.
	(copy_string_to_obstack): New function.
	(inspect_type): New function.
	(replace_typedefs): New function.
	(replace_typedefs_qualified_name): New function.
	(cp_canonicalize_string_no_typedefs): New function.
	* cp-name-parser.y (cp_merge_demangle_parse_infos): New function.
	(cp_new_demangle__parse_info): Allocate and initialize the obstack.
	* linespec.c (find_methods): Use cp_canonicalize_string_no_typedefs
	instead of cp_canonicalize_string.
	(find_method): Likewise.
	(decode_compound): Before looking up the name, call
	cp_canonicalize_string_no_typedefs.
	(decode_variable): Likewise.