sqlite3_create_functoin_v2 comment

sqlite3_create_function_v2.c

int sqlite3_create_function_v2(
  sqlite3 *db, // db connection
  const char *zFunctionName, // function name
  int nArg, // number of argument this function takes. -1 for arbitrary numbers 
  int eTextRep, // text encoding, e.g. SQLITE_UTF8 or SQLITE_ANY
  void *pApp, // pinter to function context
  void (*xFunc)(sqlite3_context*,int,sqlite3_value**), // a scalar function implementation
  void (*xStep)(sqlite3_context*,int,sqlite3_value**), // a aggregate function implementation
  void (*xFinal)(sqlite3_context*), // the same pointer with previous one
  void(*xDestroy)(void*) // destroy function context
);