Write debug output on travis

This should make it easier to debug issues when they fail on travis.
But at the sime time it also decreases the SNR and increases test times.
Will have to check if this makes sense in the long run.

Author: m-kuhn

ci/travis/linux/install.sh

@@ -2,7 +2,8 @@ mkdir build
 cd build
 export CXX="clang++-3.7"
 export CC="clang-3.7"
-cmake -DWITH_SERVER=ON \
+cmake -DCMAKE_BUILD_TYPE=RelWithDebInfo \
+      -DWITH_SERVER=ON \
       -DWITH_STAGED_PLUGINS=OFF \
       -DWITH_GRASS=ON \
       -DSUPPRESS_QT_WARNINGS=ON \