Provide a ssl3_get_cipher_by_id() function that allows ciphers to be looked

Provide a ssl3_get_cipher_by_id() function that allows ciphers to be looked
up by their ID. For one, this avoids an ugly mess in ssl_sess.c, where the
cipher value is manually written into a buffer, just so the cipher can be
located using ssl3_get_cipher_by_char().

ok bcook@ miod@