gold: fix race in FileRead::~View.

gold: fix race in FileRead::~View.

gold/:
	* fileread.cc (file_counts_lock, file_counts_initialize_lock)
	(total_mapped_bytes, current_mapped_bytes, maximum_mapped_bytes):
	Move definition before File_read::View member definitions.
	(File_read::View::~View): Initialize and hold lock before
	updating current_mapped_bytes.