Travis: updated packages to build Viewer plugin

Since ubuntu trusty, there is no default package libglui-dev.

Author: Clement Champetier

.travis.yml

@@ -113,7 +113,7 @@ addons:
     - libyaml-dev
     - libopenctl0.8
     - libcaca-dev
-    - libglui-dev
+    - freeglut3-dev
     - libtinyxml-dev
     - yasm
     - libx264-dev