MSCHAPv2 & NTLMv1: Emit a warning after loading 100 c/r pairs, informing
about slow loading and alternative formats. Re-introduce the old versions
as mschapv2-naive and netntlmv1-naive. Also fix the DES caching in NETNTLM:
it may be called from prepare() so the cache must be checked not only in
binary() but also in valid().