public FunctionInfo registerMacro(String macroName, ExprNodeDesc body,
      List<String> colNames, List<TypeInfo> colTypes, FunctionResource... resources) {
    GenericUDFMacro macro = new GenericUDFMacro(macroName, body, colNames, colTypes);
    FunctionInfo fI = new FunctionInfo(FunctionType.TEMPORARY, macroName, macro, resources);
    addFunction(macroName, fI);
    return fI;
  }
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