EP_TotSp ($1E) - Return amount of used file space in slot C

IN:
   A = EP_TOTSP
   C = slot number containing File Eprom Area

OUT:
   Fc = 0, File Eprom available
        BHL = Amount of active file space in bytes (24bit integer, B = MSB)
        CDE = Amount of deleted file space in bytes (24bit integer, C = MSB)

   Fc = 1,
        A = RC_ONF
        File Eprom was not found in slot C.

Registers changed after return:
   ......../IXIY same
   AFBCDEHL/.... different