algorithms.c, knock-on: Eliminate `f_freeme' flags.

algorithms.c, knock-on: Eliminate `f_freeme' flags.

These were being carefully set and checked on ciphers, hashes, and MACs,
for no good reason because the flag was always set.  Abolish it.

The flag still exists for `grand' objects because they get injected into
Python through the `pgen' event-handling machinery, and Python mustn't
destroy them just because it loses its reference.  (It also mustn't try
to hang onto them, so there's a longstanding bug in there.)