OpenSSL doesn't support using BIOs of the "fd" or "file" type when it is
built as a DLL and the executable didn't provide it with access to the
executable's CRT. Requiring all applications that wish to use security
to worry about this "applink.c" thing is too onerous a requirement.
* Check for the existence of "applink.c" in the OpenSSL include
directory, adding it to the security tests if it exists. This way,
all of OpenSSL can be used by the tests.
* Include it in the security core and built-in plugin tests. This way,
the test code can use the entirety of OpenSSL.
* In the authentication and access-control plugins, load X509 and
private keys from files by first reading them into a "mem" type BIO,
then reading them from that BIO.
* Take care not to call ddsrt_free on OpenSSL-allocated memory, either
by calling OPENSSL_free, or by allocating the memory using
ddsrt_malloc and letting OpenSSL fill that buffer.
Signed-off-by: Erik Boasson <eb@ilities.com>