Creates a SQL mapping routine that matches the WITH LIMIT OF
    clause for the storage map. The routine is automatically created
    in the system module RDB$STORAGE_MAPS (use SHOW SYSTEM MODULES to
    view). The storage map name is used to name the mapping routine
    (use SHOW SYSTEM FUNCTIONS to view).

                                   NOTE

       If a routine already exists with the same name as the
       storage map, then the mapping routine will not be created.

       If the storage map includes a STORE COLUMNS clause, that is,
       a vertically partitioned map, then several routines will be
       created and uniquely named by adding the vertical partition
       number as a suffix.

    The mapping routine returns the following values:

    o  Zero (0) if the storage map is defined as RANDOMLY ACROSS.
       This routine is just a descriptive place holder.

    o  Positive value representing the storage map number (the
       same value as stored in RDB$ORDINAL_POSITION column of the
       RDB$STORAGE_MAP_AREAS table). These values can be used with
       the PARTITION clause of the SET TRANSACTION...RESERVING clause
       to reserve a specific partition prior to inserting the row.

    o  A value of -1 if the storage map has no OTHERWISE clause. This
       indicates that the row cannot be inserted because it does not
       match any of the WITH LIMIT OF clauses.