Add ALPN tests to ssl-opt.sh

Only self-op for now, required peer versions are a bit high:
- OpenSSL 1.0.2-beta
- GnuTLS 3.2.0 (released 2013-05-10) (gnutls-cli only)
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 2cbc798..08f6eea 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -1450,7 +1450,7 @@
 
 #if defined(POLARSSL_SSL_ALPN)
         case TLS_EXT_ALPN:
-            SSL_DEBUG_MSG( 3, ( "found ALPN extension" ) );
+            SSL_DEBUG_MSG( 3, ( "found alpn extension" ) );
 
             ret = ssl_parse_alpn_ext( ssl, ext + 4, ext_size );
             if( ret != 0 )
@@ -1708,7 +1708,7 @@
         return;
     }
 
-    SSL_DEBUG_MSG( 3, ( "server hello, alpn extension" ) );
+    SSL_DEBUG_MSG( 3, ( "server hello, adding alpn extension" ) );
 
     /*
      * 0 . 1    ext identifier