More file existence/length checks, with only a WARNING log level (not error) since some QWKnet nodes apparently like to start concurrent QWK packet downloads and inevitably one finishes first, deleting the file, and the second transfer logs and error. Examples:
  8/14  08:10:06p  2296 <EPHRAM> downloading QWK packet (1320 bytes) in passive mode
  8/14  08:10:06p  3792 <EPHRAM> downloading QWK packet (1320 bytes) in passive mode
  8/14  08:10:06p  2296 <EPHRAM> DATA Transfer successful: 1320 bytes sent in 0 seconds (2640 cps)
  8/14  08:10:06p  3792 <EPHRAM> !DATA ERROR 2 (No such file or directory) line 1376 opening s:\sbbs\data\file/0888.qwk
  8/14  11:28:55p  2576 <POTOGOLD> downloading QWK packet (27129 bytes) in passive mode
  8/14  11:28:55p  2576 <POTOGOLD> DATA Transfer successful: 27129 bytes sent in 0 seconds (54258 cps)
  8/14  11:28:55p  1924 <POTOGOLD> downloading QWK packet (4294967295 bytes) in passive mode
  8/14  11:28:56p  1924 <POTOGOLD> !DATA ERROR 2 (No such file or directory) line 1376 opening s:\sbbs\data\file/0168.qwk

Also some more 64-bit file length support (flength returns an off_t now, not a ulong).
And ftell() returns a long (not a ulong).