* ext/openssl/extconf.rb: Check existence of accessor functions that
don't exist in OpenSSL 0.9.8. OpenSSL 1.1.0 made most of its
structures opaque and requires use of these accessor functions.
[ruby-core:75225] [Feature #12324]
* ext/openssl/openssl_missing.[ch]: Implement them if missing.
* ext/openssl/ossl*.c: Use these accessor functions.
* test/openssl/test_hmac.rb: Add missing test for HMAC#reset.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@55287 b2dd03c8-39d4-4d8f-98ff-823fe69b080e