Rich -

As discussed on IRC, here is a revision of the FreeSec crypt() code with
greatly reduced memory requirements: 10 KB for the "shared" and "local"
structs combined.  The original code required about 70 KB of .bss.

This passes the included tests, but more testing is desired - perhaps
fuzz this on random passwords/salts against other implementations.

Also, we could want to add a runtime self-test, which would detect
possible miscompiles.

Oh, and I haven't yet replaced the cast to signed char in ascii_to_bin().

Anyway, this should be better than what's currently in musl.

Alexander