MPI: Add signaling of cracked hashes. There is also various changes to
the handling of --fork sessions in this regard.
Drop the experimental --reload-every=N option. We always reload
at session save (unless totally disabled in john.conf).
Do not re-read pot file lines that were processed by initial loading.
Drop an unneeded strnzcpy() during reload of pot file. Also adds debug
stuff to crk_reload_pot().
Pause/abort on filesystem stimuli. This defaults to /var/run/john/abort
and /var/run/john/pause but can be reconfigured to any other files.

Files are polled every 3 seconds.
Recent structural changes and new features introduced some terrific bugs.
This hopefully fixes most of them.
Speed up pot reload (a lot) by using bitmap.
#ifdef out some select() stuff in tty_getchar() that was used for
Cygwin but isn't needed (anymore?).
"Reload" code cleanup and optimizations.
Less timid --max-runtime: We now give a 3 sec grace period and then
force quit as if ctrl-c was pressed twice.
Keep loader's salt hash table for pot reload (updating it w/ required).
The documentation of --save-memory was duplicated in doc/OPTIONS.
Don't keep salt hash table if --save-memory=2 or greater, or if the
format doesn't have a salt_hash function anyway.  Update salt hash table
after sorting (if applicable).  Add some safety measures to pot reload.
Add some OSX building tips to docs.
Update to hi res timer code.
Pot reload: In Single mode there may be dupes, so in that case we
search for them.
Add options to john.conf for defaults and batch mode
- Single mode rules
- Wordlist rules
- Incremental mode
Add a build target for win64-cygwin-x86-64-opencl and drop -static from Cygwin64.
Various minor tweaks, and Jumbo code cleanup in loader.c (overlong lines).
Optimizations (some were really bug fixes, but they only affected
performance) for pot reload.