crypto: improve error messages

1) ThrowCryptoTypeErrors was not actually used for
   type-related errors. Removed it.
2) For AEAD modes, OpenSSL does not set any internal
   error information if Final does not complete suc-
   cessfully. Therefore, "TypeError:error:00000000:l
   ib(0):func(0):reason(0)" would be the error mess-
   age. Use a default message for these cases.

Signed-off-by: Fedor Indutny <fedor@indutny.com>