Test dtls_server

Test against both OpenSSL and GnuTLS.

Don't use a proxy. It's not particularly useful here, and would complicate
figuring out port numbers.

Clean up compile-time requirements dtls_server.c: any certificate-based key
exchange is ok, so don't insist on built-in RSA.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 1b5931c..b32c63c 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -500,6 +500,7 @@
             requires_config_enabled MBEDTLS_SSL_CLI_C
             requires_certificate_authentication
             ;;
+        *"programs/ssl/dtls_server "*|\
         *"programs/ssl/ssl_fork_server "*|\
         *"programs/ssl/ssl_pthread_server "*|\
         *"programs/ssl/ssl_server "*)
@@ -1277,7 +1278,7 @@
 # check if the given command uses dtls and sets global variable DTLS
 detect_dtls() {
     case "$1" in
-        *dtls=1*|*-dtls*|*-u*) DTLS=1;;
+        *dtls=1*|*-dtls*|*-u*|*/dtls_*) DTLS=1;;
         *) DTLS=0;;
     esac
 }