[travis] switch to my own llvm ppa mirror

.travis.yml

@@ -39,6 +39,8 @@ before_install:
   - sudo -E apt-get install -y -q python-pip python3-pip
   - sudo -E pip3 install -U requests virtualenv cpp-coveralls
   - sudo -E pip install -U requests virtualenv cpp-coveralls
+  - sudo -E add-apt-repository -y ppa:renemilk/llvm 
+  - sudo -E apt-get update -qq && sudo -E aptitude install -y clang-3.7 clang-format-3.7
   - export PATH=/usr/lib/ccache:$PATH
   - cd $HOME
   - test -d src || git clone https://github.com/dune-community/dune-xt-super.git src
@@ -156,10 +158,9 @@ matrix:
         apt:
           sources:
           - *commonsources
-          - ['ubuntu-toolchain-r-test', 'llvm-toolchain-precise-3.7']
+          - ['ubuntu-toolchain-r-test']
           packages:
           - *commonpackages
-          - ['clang-3.7', 'clang-format-3.7']
       env: CXX=clang++-3.7 CC=clang-3.7 MODULES_TO_DELETE="dune-xt-grid dune-xt-la dune-xt-functions" CLANG_FORMAT="/usr/bin/clang-format-3.7"
 
     - os: linux
@@ -167,10 +168,9 @@ matrix:
         apt:
           sources:
           - *commonsources
-          - ['ubuntu-toolchain-r-test', 'llvm-toolchain-precise-3.7']
+          - ['ubuntu-toolchain-r-test'] 
           packages:
           - *commonpackages
-          - ['clang-3.7']
       # fake last module to delete to distinguish testlogs
       env: OPTS=config.opts/travis.make BUILD_CMD="make -k -j2" CXX=clang++-3.7 CC=clang-3.7 MODULES_TO_DELETE="dune-xt-grid dune-xt-la dune-xt-functions with-make"