data: Structure for file buffers for merge index

mf_num_files    equ     50              ;number of files we support during
                                        ; a merge
mf_buffer       equ     0               ;pointer to beginning of buffer
mf_pointer      equ     4               ;pointer to current record within
                                        ; block
mf_open         equ     8               ;TRUE | FALSE whether the file is
                                        ; open or not
mf_handle       equ     10              ;DOS file handle
mf_filename     equ     12              ;full pathname here...
mf_active       equ     100             ;if FALSE, then this area is no longer
                                        ; used
mf_records      equ     102             ;number of records in memory
mf_read         equ     106             ;if FALSE, then do NOT read any more
                                        ; from tmp file and set active to FALSE
mf_rw_ptr       equ     108             ;rw pointer for tmp file for reread
mf_table_len    equ     112