public FunctionInfo registerGenericUDTF(String functionName,
      Class<? extends GenericUDTF> genericUDTFClass, FunctionResource... resources) {
    FunctionType functionType = isNative ? FunctionType.BUILTIN : FunctionType.TEMPORARY;
    return registerGenericUDTF(functionName, functionType, genericUDTFClass, resources);
  }
Registers the UDF class as a built-in function; used for dynamically created UDFs, like
GenericUDFOP*Minus/Plus.
ql/src/java/org/apache/hadoop/hive/ql/exec/Registry.java