sqlite3: fix build when threads are not used/available

When threads are not used/available, a function in the sqlite3 extension
ends up with a label at the end:

    void _pysqlite_final_callback(sqlite3_context* context)
    {
        PyObject* function_result;
        PyObject** aggregate_instance;
        int ok;

    #ifdef WITH_THREAD
        PyGILState_STATE threadstate;

        threadstate = PyGILState_Ensure();
    #endif

        aggregate_instance = (PyObject**)sqlite3_aggregate_context(context, sizeof(PyObject*));
        if (!*aggregate_instance) {
            goto error;
        }

        [......]

    error:
    #ifdef WITH_THREAD
        PyGILState_Release(threadstate);
    #endif
    }

This is not valid, and gcc complains.

Fix that by adding a dummy statement after the label, so that the label
is never the last statement of the function.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

Index: b/Modules/_sqlite/connection.c
===================================================================
--- a/Modules/_sqlite/connection.c
+++ b/Modules/_sqlite/connection.c
@@ -786,6 +786,7 @@
 #ifdef WITH_THREAD
     PyGILState_Release(threadstate);
 #endif
+    ;   /* Make gcc happy: a label can't be at the end of a function */
 }
 
 static void _pysqlite_drop_unused_statement_references(pysqlite_Connection* self)