Add EVP_CIPHER_meth_* documentation from OpenSSL 1.1

Add EVP_CIPHER_meth_* documentation from OpenSSL 1.1

This is essentially the original text with a few tweaks and fixes by me,
removing parts inapplicable to LibreSSL. There are dangling references to
EVP_CIPHER_CTX_copy(3) and EVP_CIPHER_CTX_get_cipher_data(3). This all
isn't great, but it's better than nothing. Probably good enough for these
rarely used functions.