chore(ci): update travis to ubuntu 16.04, since 14.04 is EOL

Ubuntu has Qt 5.5.1 in its repos, so PPA is no longer required.

.travis.yml

@@ -1,5 +1,5 @@
 sudo: required
-dist: trusty
+dist: xenial
 language: cpp
 cache: ccache
 
@@ -44,7 +44,7 @@ jobs:
     # the actual compilin'
     - stage: Linux
       os: linux
-      env: JOB=build-ubuntu-14-04
+      env: JOB=build-ubuntu-16-04
       script: "./.travis/$JOB.sh"
     - stage: "Windows Stage 1: Dependencies (OpenSSL, Qt)"
       os: linux

.travis/build-ubuntu-16-04.sh

@@ -19,8 +19,6 @@
 # stop as soon as one of steps will fail
 set -e -o pipefail
 
-# Qt 5.5, since that's the lowest supported version
-sudo add-apt-repository -y ppa:beineri/opt-qt551-trusty
 sudo apt-get update -qq
 
 # install needed Qt, OpenAL, opus, qrencode, GTK tray deps, sqlcipher
@@ -43,16 +41,13 @@ sudo apt-get install -y --force-yes \
     libtool \
     libvpx-dev \
     libxss-dev qrencode \
-    qt55base \
-    qt55script \
-    qt55svg \
-    qt55tools \
-    qt55xmlpatterns \
+    qt5-default \
+    qttools5-dev-tools \
+    qttools5-dev \
+    libqt5opengl5-dev \
+    libqt5svg5-dev \
     pkg-config || yes
 
-# Qt
-source /opt/qt55/bin/qt55-env.sh || yes
-
 # ffmpeg
 if [ ! -e "libs" ]; then mkdir libs; fi
 if [ ! -e "ffmpeg" ]; then mkdir ffmpeg; fi

tools/update-toxcore-version.sh

@@ -60,7 +60,7 @@ update_flatpak() {
 
 update_travis() {
     cd .travis
-    perl -i -0pe "s|$VERSION_PATTERN( --depth=1 https://github.com/toktok/c-toxcore)|$@\${1}|gms" build-ubuntu-14-04.sh
+    perl -i -0pe "s|$VERSION_PATTERN( --depth=1 https://github.com/toktok/c-toxcore)|$@\${1}|gms" build-ubuntu-16-04.sh
     cd ..
 }