Add mapppings in POSTPROC field of a datafile
A = ADDPOSTPROC(A,MAPPING)
Extends the set of mappings stored in A.POSTPROC. Existing mappings are extended sequentially
A.POSTPROC = A.POSTPROC * MAPPING
Mappings in A.POSTPROC are stored only and executed just after A is converted from a DATAFILE into a PRDATASET. The feature size of the datafile A is reset to the output size of PRMAPPING. The POSTPROC field of A can be reset by SETPOSTPROC.