CI: Updated Travis build configuration

.travis.yml

@@ -2,25 +2,14 @@
 language: cpp
 os: linux
 sudo: required
-dist: trusty
+dist: xenial
 cache: ccache
 
 before_install:
-    - sudo add-apt-repository ppa:zoogie/sdl2-snapshots -y
-    - sudo add-apt-repository ppa:beineri/opt-qt551-trusty -y
-    - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
-    - sudo apt-get -qq update
-    - if [ "$CXX" = "g++" ]; then sudo apt-get install -qq g++-4.9; fi
-    - if [ "$CXX" = "g++" ]; then export CXX="g++-4.9" CC="gcc-4.9"; fi
-    - sudo apt-get -y install cmake libsdl2-dev libsdl2-mixer-dev libxrandr-dev libxxf86vm-dev libfluidsynth-dev ncurses-dev 
-    - sudo apt-get -y install qt55base qt55imageformats qt55x11extras
+    - sudo apt-get -y install cmake libsdl2-dev libsdl2-mixer-dev libxrandr-dev libxxf86vm-dev libfluidsynth-dev ncurses-dev qt5-default libqt5x11extras5
 
 before_script:
     - mkdir build-travis
 
 script:
-    - source /opt/qt55/bin/qt55-env.sh
-    - cd build-travis && cmake -DQMAKE=/opt/qt55/bin/qmake -DCMAKE_BUILD_TYPE=RelWithDebInfo -DDENG_ENABLE_TESTS=ON ../doomsday && make -j4
-
-notifications:
-    slack: dengteam:A4Hl4awsyxNxQG61rrWgDuHo
+    - cd build-travis && cmake -DCMAKE_BUILD_TYPE=RelWithDebInfo -DDENG_ENABLE_TESTS=ON ../doomsday && make -j4