Contrib: updated libiax rules to new tarball contents

The directory name inside the tarball has changed. This
commit adapts the build system to the new directory name.
We also pin the version so that the contrib does not break
if the repository is ever updated.

Tuleap: #670
Change-Id: I973505eb7dec31591e382ac697f9527097399b27

contrib/src/iax/rules.mak

 #IAX
 
-IAX_URL = https://gitlab.savoirfairelinux.com/sflphone/libiax2/repository/archive.tar.gz
+IAX_VERSION = 0e5980f1d78ce462e2d1ed6bc39ff35c8341f201
+IAX_URL = https://gitlab.savoirfairelinux.com/sflphone/libiax2/repository/archive.tar.gz?ref=$(IAX_VERSION)
 
 PKGS += iax
 
@@ -13,7 +14,7 @@ $(TARBALLS)/iax-git.tar.gz:
 
 iax: iax-git.tar.gz .sum-iax
 	$(UNPACK)
-	mv libiax2.git $@
+	mv libiax2-$(IAX_VERSION)-$(IAX_VERSION) $@
 	touch $@