aarch64: Fix function multiversioning mangling

aarch64: Fix function multiversioning mangling

It would be neater if the middle end for target_clones used a target
hook for version name mangling, so we only do version name mangling
once.  However, that would require more intrusive refactoring that will
have to wait till Stage 1.

gcc/ChangeLog:

	* config/aarch64/aarch64.cc (aarch64_mangle_decl_assembler_name):
	Move before new caller, and add ".default" suffix.
	(get_suffixed_assembler_name): New.
	(make_resolver_func): Use get_suffixed_assembler_name.
	(aarch64_generate_version_dispatcher_body): Redo name mangling.

gcc/testsuite/ChangeLog:

	* g++.target/aarch64/mv-symbols1.C: New test.
	* g++.target/aarch64/mv-symbols2.C: Ditto.
	* g++.target/aarch64/mv-symbols3.C: Ditto.
	* g++.target/aarch64/mv-symbols4.C: Ditto.
	* g++.target/aarch64/mv-symbols5.C: Ditto.
	* g++.target/aarch64/mvc-symbols1.C: Ditto.
	* g++.target/aarch64/mvc-symbols2.C: Ditto.
	* g++.target/aarch64/mvc-symbols3.C: Ditto.
	* g++.target/aarch64/mvc-symbols4.C: Ditto.