Throw errors when using variable-length arrays

Windows already complains about this in CI, but this will
let us catch these issues on Linux as well.

Windows already complains about this in CI, but this will
let us catch these issues on Linux as well.

Thanks to Stefan Kölbl

Detect cron builds on Travis CI

Make diffs in dup_consistency files part of scheme

Previously, changing a duplicate_consistency file would be
considered a 'global' change, resulting in CI re-running all tests
for all schemes.

Schedules circleci builds with RUN_SLOW

Be more selective in test runs

Also specifies an order on the PQCLEAN builds to limit fruitless
testing.

Move secret key length back to scheme-level META

This way we can properly raise skiptest

Slow tests

Add -O3 to CFLAGS