SSL_CTX_free() decrements the reference count of ctx, and removes the SSL_CTX object pointed to
by ctx and frees up the allocated
memory if the the reference count has reached 0.
It also calls the free()ing procedures for indirectly affected items,
if applicable: the session cache, the list of ciphers, the list of
Client CAs, the certificates and keys.
WARNINGS
If a session-remove callback is set (SSL_CTX_sess_set_remove_cb()),
this callback will be called for each session being freed from
ctx's session cache. This implies,
that all corresponding sessions from an external session cache are
removed as well. If this is not desired, the user should explicitly
unset the callback by calling SSL_CTX_sess_set_remove_cb(ctx, NULL) prior to calling SSL_CTX_free().
RETURN VALUES
SSL_CTX_free() does not provide diagnostic information.
