Do locking for __gcov_dump and __gcov_reset as well.

	PR gcov-profile/93623
	* Makefile.in: Add _gcov_lock_unlock to LIBGCOV_INTERFACE.
	* libgcov-interface.c (ALIAS_void_fn): Remove.
	(__gcov_lock): New.
	(__gcov_unlock): New.
	(__gcov_flush): Use __gcov_lock and __gcov_unlock.
	(__gcov_reset): Likewise.
	(__gcov_dump): Likewise.
	* libgcov.h (__gcov_lock): New declaration.
	(__gcov_unlock): Likewise.