travis.yml: forcing clang 3.4

.travis.yml

@@ -7,11 +7,15 @@ compiler:
 before_install:
   - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
   - sudo apt-get update -qq
-  - if [ "$CXX" = "clang++" ]; then sudo apt-get install -qq libstdc++-4.9-dev; fi
+  - if [ "$CXX" = "clang++" ]; then sudo apt-get install -qq libstdc++-4.9-dev clang-3.4; fi
+  - if [ "$CXX" = "clang++" ]; then export CXX="clang++-3.4.0" CC="clang-3.4.0"; fi
   - if [ "$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
   - apt-cache search clang
+  - ls /usr/bin/clang*
   - apt-cache search gcc
+  - ls /usr/bin/gcc*
+  - ls /usr/bin/g++*
 
 env:
   - BUILD_TYPE=Debug