Fix compilation errors in zim_Phalcon_Mvc_Model_Row_toArray()

```
/home/vladimir/workspace/cphalcon/ext/mvc/model/row.c: In function ‘zim_Phalcon_Mvc_Model_Row_toArray’:
/home/vladimir/workspace/cphalcon/ext/mvc/model/row.c:159:13: error: assignment from incompatible pointer type [-Werror]
  properties = Z_OBJ_HT_P(this_ptr)->get_properties(this_ptr TSRMLS_CC);
             ^
/home/vladimir/workspace/cphalcon/ext/mvc/model/row.c:167:2: error: passing argument 1 of ‘zend_hash_internal_pointer_reset_ex’ from incompatible pointer type [-Werror]
  zend_hash_internal_pointer_reset_ex(properties, &hp0);
  ^
In file included from /home/vladimir/.phpenv/versions/5.5.4-debug-zts/include/php/Zend/zend.h:286:0,
                 from /home/vladimir/.phpenv/versions/5.5.4-debug-zts/include/php/main/php.h:34,
                 from /home/vladimir/workspace/cphalcon/ext/mvc/model/row.c:24:
/home/vladimir/.phpenv/versions/5.5.4-debug-zts/include/php/Zend/zend_hash.h:183:15: note: expected ‘struct HashTable *’ but argument is of type ‘struct zval *’
 ZEND_API void zend_hash_internal_pointer_reset_ex(HashTable *ht, HashPosition *pos);
               ^
/home/vladimir/workspace/cphalcon/ext/mvc/model/row.c:168:2: error: passing argument 1 of ‘zend_hash_get_current_data_ex’ from incompatible pointer type [-Werror]
  while (zend_hash_get_current_data_ex(properties, (void**) &hd, &hp0) == SUCCESS) {
  ^
In file included from /home/vladimir/.phpenv/versions/5.5.4-debug-zts/include/php/Zend/zend.h:286:0,
                 from /home/vladimir/.phpenv/versions/5.5.4-debug-zts/include/php/main/php.h:34,
                 from /home/vladimir/workspace/cphalcon/ext/mvc/model/row.c:24:
/home/vladimir/.phpenv/versions/5.5.4-debug-zts/include/php/Zend/zend_hash.h:182:14: note: expected ‘struct HashTable *’ but argument is of type ‘struct zval *’
 ZEND_API int zend_hash_get_current_data_ex(HashTable *ht, void **pData, HashPosition *pos);
              ^
/home/vladimir/workspace/cphalcon/ext/mvc/model/row.c:169:3: error: implicit declaration of function ‘phalcon_get_current_key’ [-Werror=implicit-function-declaration]
   PHALCON_GET_HKEY(key, ah0, hp0);
   ^
cc1: all warnings being treated as errors
make: *** [mvc/model/row.lo] Помилка 1
```