demangler: C++ modules support

demangler: C++ modules support

This adds demangling support for C++ modules.  A new 'W' component
along with augmented behaviour of 'S' components.

	include/
	* demangle.h (enum demangle_component_type): Add module components.
	libiberty/
	* cp-demangle.c (d_make_comp): Adjust.
	(d_name, d_prefix): Adjust subst handling. Add module handling.
	(d_maybe_module_name): New.
	(d_unqualified_name): Add incoming module parm. Handle it.  Adjust all callers.
	(d_special_name): Add 'GI' support.
	(d_count_template_scopes): Adjust.
	(d_print_comp_inner): Print module.
	* testsuite/demangle-expected: New test cases