The $XABPRO_STORE macro moves user-specified values into fields
    of the specified XABPRO. The expanded $XABPRO_STORE code executes
    at run time on a previously initialized (allocated) XABPRO, in
    contrast to the $XABPRO macro, which initializes a XABPRO at
    assembly time. The $XABPRO_STORE macro must reside in a code
    program section.
    Format
      $XABPRO_STORE  XAB=xabpro-address,
                     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=#uic-value