New SSL test framework

Currently, SSL tests are configured via command-line switches to
ssltest.c. This results in a lot of duplication between ssltest.c and
apps, and a complex setup. ssltest.c is also simply old and needs
maintenance.

Instead, we already have a way to configure SSL servers and clients, so
we leverage that. SSL tests can now be configured from a configuration
file. Test servers and clients are configured using the standard
ssl_conf module. Additional test settings are configured via a test
configuration.

Moreover, since the CONF language involves unnecessary boilerplate, the
test conf itself is generated from a shorter Perl syntax.

The generated testcase files are checked in to the repo to make
it easier to verify that the intended test cases are in fact run; and to
simplify debugging failures.

To demonstrate the approach, min/max protocol tests are converted to the
new format. This change also fixes MinProtocol and MaxProtocol
handling. It was previously requested that an SSL_CTX have both the
server and client flags set for these commands; this clearly can never work.

Guide to this PR:
 - test/ssl_test.c - test framework
 - test/ssl_test_ctx.* - test configuration structure
 - test/handshake_helper.* - new SSL test handshaking code
 - test/ssl-tests/ - test configurations
 - test/generate_ssl_tests.pl - script for generating CONF-style test
   configurations from perl inputs

Reviewed-by: Richard Levitte <levitte@openssl.org>