Defines a procedure descriptor structure at the current psect and
    offset.

    Format

      $PROCEDURE_DESCRIPTOR

1  –  Description

    The arguments for the $PROCEDURE_DESCRIPTOR macro are the same as
    the $ROUTINE macro, with the following exceptions:

    o  The ENTRY argument is required.

    o  There are no CODE_SECTION, LINKAGE_SECTION, DATA_SECTION,
       DATA_SECTION_POINTER, or STANDARD_PROLOGUE arguments.

    o  There is an additional END_PROLOGUE argument. This argument
       must be a label that you define at the end of the routine's
       prologue sequence. This argument is required for stack and
       register procedure types.

2  –  Notes

    o  Because the $ROUTINE macro invokes the $PROCEDURE_DESCRIPTOR
       macro for you, you do not need to use the
       $PROCEDURE_DESCRIPTOR macro if you use $ROUTINE. You may wish
       to use $PROCEDURE_DESCRIPTOR when you are not using $ROUTINE.

3  –  Example

            $PROCEDURE_DESCRIPTOR p1,           -
                              KIND=NULL,        -
                              ENTRY=p1_entry