remove unused dynamic_cmd_defns_empty structure.

ok miod@ deraadt@ guenther@
Remove RSA_memory_lock(). This undocumented function sort-of serializes your
RSA components to memory and clears them, but there is no unserializing
function, so its usefulness is close to zero.

A grep through the ports tree sources show that it is only present in ports
embedding their own openssl copy, and never used otherwise.

ok jsing@
In the old days (not in this century), SSLeay 0.4.5 would create X.509 RSA
signatures using the wrong oid for the signature type. The signature
verification code has thus been modified to allow these signatures to be
accepted, with a printf to stderr to notify the user something was fishy.

Remove this chunk; these signatures will no longer get accepted.
ok deraadt@ guenther@ jsing@ tedu@
Remove typecasts on password_callback.

Rather than casting password_callback to the correct function pointer
signature at every call site, change it to match the signature instead.

ok miod@ deraadt@ tedu@
Be more strict in RSA_padding_check_X931(), and thus avoid a possible
memcpy() with a negative size.
ok tedu@