The $XABPRO macro allocates and initializes a XABPRO. No value is
    returned for this assembly-time operation.

    Format

      $XABPRO  ACLBUF=ACL-buffer-address,

               ACLCTX=<ACL-context>,

               ACLSIZ=ACL-buffer-size,

               MTACC=magnetic-tape-accessibility,

               NXT=next-xab-address,

               PRO=<system, owner, group, world>,

               PROT_OPT=<PROPAGATE>,

               UIC=<group, member>