contrib: force gnutls minimal version to 3.3.19

3.3.19 of gnutls is the one containing a patch to be able
to make a anon to RSA re-negotiation.
This is needed by commit fbdc7b24.

Change-Id: Ie63657031b0f8f3f50d98eda14e6dd47e64ac559
Tuleap: #526

contrib/src/gnutls/rules.mak

@@ -4,7 +4,7 @@ GNUTLS_VERSION := 3.4.10
 GNUTLS_URL := ftp://ftp.gnutls.org/gcrypt/gnutls/v3.4/gnutls-$(GNUTLS_VERSION).tar.xz
 
 PKGS += gnutls
-ifeq ($(call need_pkg,"gnutls >= 3.3.0"),)
+ifeq ($(call need_pkg,"gnutls >= 3.3.19"),)
 PKGS_FOUND += gnutls
 endif