In evp.h rev. 1.56 2018/02/17 14:55:31, jsing@ provided

In evp.h rev. 1.56 2018/02/17 14:55:31, jsing@ provided
EVP_MD_CTX_new(3), EVP_MD_CTX_reset(3), and EVP_MD_CTX_free(3).
Merge the documentation from OpenSSL, tweaked by me.
Also merge a few other minor improvements from OpenSSL.

While here, improve the order of functions, improve the description
of deprecated functions, fix a few other minor bugs, and remove an
irrelevant warning about binary incompatibility.