Make kssl compile against OpenSSL 1.1.0

OpenSSL 1.1.0 contains some source-incompatible changes, most notably
making most of the structures opaque and introducing new getter/setter
functions to modify the structures. This patch adds some of the newly
introduced functions to the KOpenSSL class and modifies the code to
call them. The implementation of those newly introduced methods
contains both OpenSSL < 1.1 compatible code (direct structure member
access) and calls to real functions resolved from OpenSSL>= 1.1
library. Which implementation is used is decided at compile time. Some
of the existing methods were renamed to match the OpenSSL 1.1 naming
and to avoid conflicts with backward-compatibility names provided by
OpenSSL 1.1.

KSSLCertificate::toNetscape() returns empty result when built against
OpenSSL 1.1 since I wasn't able to find a proper equivalent in OpenSSL
1.1 API (and there does not seem to be any).

(Backport of commit 9a990c69c606126bcd60cd7718462aec2a92460d from
kdelibs4support)