PR symtab/12704

	PR symtab/12704
	* cp-namespace.c (ANONYMOUS_NAMESPACE_LEN): Remove.
	(cp_scan_for_anonymous_namespaces): Use CP_ANONYMOUS_NAMESPACE_STR
	and CP_ANONYMOUS_NAMESPACE_LEN.
	(cp_is_anonymous): Likewise.
	* cp-support.h (CP_ANONYMOUS_NAMESPACE_STR): Define.
	(CP_ANONYMOUS_NAMESPACE_LEN): Define.
	* dwarf2read.c (namespace_name): Likewise.
	(fixup_partial_die): Likewise.
	* linespec.c (decode_compound): If CP_ANONYMOUS_NAMESPACE_STR is
	seen in the input, keep it.