Alternative format for GBLx statements

The assembler permits the alternative statement format for GBLx instructions:
                                                               Cont.

         GBLA            &GLOBAL_SYMBOL_FOR_DC_GEN,              X
                         &LOOP_CONTRL_A,                         X
                         &VALUE_PASSED_TO_FIDO,                  X
                         &VALUE_RETURNED_FROM_FIDO