Add checks to the return value of EVP_Cipher to prevent silent encryption failure.

PR#1767

Reviewed-by: Richard Levitte <levitte@openssl.org>
(cherry picked from commit 244d0955adc027c0f41a3251e55d145bf940f9ce)
Check EVP_Cipher return values for SSL2

Reviewed-by: Richard Levitte <levitte@openssl.org>
(cherry picked from commit 5fc8bb6ab71b5f7ce2dd67a47494bb5b5c6dc374)
Fixed warning in ssl2_enc

Reviewed-by: Richard Levitte <levitte@openssl.org>
(cherry picked from commit 2db95e094d23b41d2305c0a01db66694ea77f936)