Add DTLS to SSL_get_version

(Imported from upstream's 504e643e0996fb842ac183023c3a6b9049af50ea)

Change-Id: I94f4fea105b6eeb001d376ca3ffef77d1432aa88
Reviewed-on: https://boringssl-review.googlesource.com/4462
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/ssl_lib.c b/ssl/ssl_lib.c
index 2d92b30..c491b12 100644
--- a/ssl/ssl_lib.c
+++ b/ssl/ssl_lib.c
@@ -2350,6 +2350,12 @@
     case SSL3_VERSION:
       return "SSLv3";
 
+    case DTLS1_VERSION:
+      return "DTLSv1";
+
+    case DTLS1_2_VERSION:
+      return "DTLSv1.2";
+
     default:
       return "unknown";
   }