Allow mit-krb5, m2crypto and python to build.

Here is a bunch of patch to reduce the set of "fails to build".
* app-crypt/mit-krb5: use fallback system already in place if building with LibreSSL
* dev-python/m2crypto: remove SSLv2_method (which is gone actually in the new sources)
* dev-lang/python: return -1 instead of RAND_egd() if using LibreSSL