Fix ReflectionMethod signatures for appendByKey,prepend, etc.

[TysonAndre]

memc_store_impl suggests that the prepend family expects exactly 3 arguments for prependByKey(), 2 for prepend(). memcached-api.php already has the correct counts (3 for byKey, 2 for plain)

1912     if (by_key) {
1913         if (op == MEMC_OP_APPEND || op == MEMC_OP_PREPEND) {
1914             if (zend_parse_parameters(ZEND_NUM_ARGS(), "SSS", &server_key, &key, &s_value) == FAILURE) {
1915                 return;
1916             }
....
1928     } else {
1929         if (op == MEMC_OP_APPEND || op == MEMC_OP_PREPEND) {
1930             if (zend_parse_parameters(ZEND_NUM_ARGS(), "SS", &key, &s_value) == FAILURE) {

Example snippet showing the bug:

(new ReflectionMethod('Memcached', 'prepend'))->getNumberOfParameters() was wrong as a result of this. It should be 2, but was 3.

[sodabrew]

You're right - and the memcached protocol explicitly states that expiration is ignored for append/pretend if it is given.