Fix miscellaneous typos in docs and source

- d2i_PKC8PrivateKey -> d2i_PKCS8PrivateKey
- bechmark -> benchmark
- ciperhsuite -> ciphersuite
- EncyptedPreMasterSecret -> EncryptedPreMasterSecret

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5570)