Autotools buildsystem

Not a particularly nice configure, some of the openssl/gmp logic might be better managed in source rather than in configure.

Otherwise, seems to work as intended. Interesting options are:
--with-openssl
--with-gmp
--with-yasm

If these are used explicitly, they are forced on. If none are specified, the best combination is chosen (I hope!). If --without-foo is used, foo will not be used even if found.