A simple execution of tmp/invoke-rename.pl

The race was due to mpi_exp_mod storing a Montgomery coefficient in the
context (RM, RP, RQ).

The fix was verified with -fsanitize-thread using ssl_pthread_server and two
concurrent clients.

A more fine-grained fix should be possible, locking just enough time to check
if those values are OK and set them if not, rather than locking for the whole
mpi_exp_mod() operation, but it will be for later.

Note from future self: actually md_init_ctx will be re-introduced with the
same signature later, and a new function with the additional argument will be
added.

- more freedom for us to change it in the future
- enforces hygiene
- performance impact of making accessors no longer inline should really be
  negligible

enumerated type mixed with another type

This reverts commit b4fae579.

Conflicts:
	library/pk.c
	tests/suites/test_suite_pk.data
	tests/suites/test_suite_pk.function