Contribs: don't hardcode URLs - 2

(cherry picked from commit 2a445ee73c918db2e1cf96da4fd6bb50de77da2b)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

contrib/src/bluray/rules.mak

 # LIBBLURAY
 
 BLURAY_VERSION := 0.6.2
-BLURAY_URL := http://ftp.videolan.org/pub/videolan/libbluray/$(BLURAY_VERSION)/libbluray-$(BLURAY_VERSION).tar.bz2
+BLURAY_URL := $(VIDEOLAN)/libbluray/$(BLURAY_VERSION)/libbluray-$(BLURAY_VERSION).tar.bz2
 
 ifdef BUILD_DISCS
 PKGS += bluray