calling RegisterAuthorizer multiple times leaks memory

When RegisterAuthorizer is called multiple times, handleVal keeps callbacks in a map until Close() is called. deleteHandles() should be called every time RegisterAuthorizer is called.

func (c *SQLiteConn) RegisterAuthorizer(callback func(int, string, string, string) int) {
	deleteHandles(c) // delete previous callback from handleVal
	if callback == nil {
		C.sqlite3_set_authorizer(c.db, nil, nil)
	} else {
		C.sqlite3_set_authorizer(c.db, (*[0]byte)(C.authorizerTrampoline), newHandle(c, callback))
	}
}

Start at the SQLiteConn.RegisterAuthorizer entry point shown in the issue and trace deleteHandles, handleVal, and newHandle. Confirm that repeated registration, including a nil callback, no longer retains the previous callback until Close(); the issue does not name a specific test or file.