Removed an overzealous optimization: we must record the entry and length in
fix_state() despite of them not changing in inc_key_loop(), because
save_state() might be called before the very first call to fix_state() from
inc_key_loop() and in that case it must record a previous entry and length.
Exclude sending of signals to child processes in DJGPP builds (untested)
If we're the main process for a --fork'ed group of children, leave our .rec
file around until the children terminate