using crashes server

When the server is configured to use a RSA key, and when the client sends
a cipher-suite list that contains a non-RSA key as acceptable, the server 
would try to process that key even though it was impossible.

Now, yaSSL sets its own acceptable-cipher list according to what kind of
key the server is started with, and will never explore and try to pair 
impossible combinations.

This involves a partial import of the current YaSSL tree, not the whole
thing, so as to try to avoid introducing new bugs.

(Updated to avoid many whitespace changes and make diff smaller.)