Allow using -SSLv2 again when setting Protocol in the config.

RT#3625

Reviewed-by: Emilia Käsper <emilia@openssl.org>
RT3497: The ticket that keeps on giving.

Don't remove c_rehash that wasn't created by make; this script
is created by configure.

This fix brought to you by the letter "f" and
Reviewed-by: Emilia Kasper <emilia@openssl.org>