Install doxygen 1.8.14 on travis

Author: peterschrammel

.travis.yml

@@ -53,9 +53,9 @@ jobs:
             - sourceline: 'deb http://packages.cloud.google.com/apt cloud-sdk-trusty main'
               key_url: 'https://packages.cloud.google.com/apt/doc/apt-key.gpg'
           packages:
-            - doxygen
             - google-cloud-sdk
       install:
+        - wget http://ftp.stack.nl/pub/users/dimitri/doxygen-1.8.14.src.tar.gz; tar xfz doxygen-1.8.14.src.tar.gz; cd doxygen-1.8.14; ./configure; make; cd ..; export PATH=$PATH:`pwd`/doxygen-1.8.14/bin; echo $PATH; doxygen --version
       script: scripts/travis_doxygen.sh
       before_cache:
       after_success: