Fix duplicates for anonymous structures with -fdump-ada-spec

Fix duplicates for anonymous structures with -fdump-ada-spec

This fixes a weakness in the way -fdump-ada-spec builds names for
anonymous structures in the C/C++ code, resulting in duplicate
identifiers under specific circumstances.

c-family/
	* c-ada-spec.c: Include bitmap.h.
	(dump_ada_double_name): Rename into...
	(dump_anonymous_type_name): ...this.  Always use the TYPE_UID.
	(dump_ada_array_type): Adjust to above renaming.  Robustify.
	(dump_nested_types_1): New function copied from...  Add
	dumped_types parameter and pass it down to dump_nested_type.
	(dump_nested_types): ...this.  Remove parent parameter.  Just
	call dump_nested_types_1 on an automatic bitmap.
	(dump_nested_type): Add dumped_types parameter.
	<ARRAY_TYPE>: Do not dump it if already present in dumped_types.
	Adjust recursive calls and adjust to above renaming.
	(dump_ada_declaration): Adjust call to dump_nested_types.
	Tidy up and adjust to above renaming.
	(dump_ada_specs): Initialize and release bitmap obstack.