TRAVIS: install latest doxygen, also install graphviz

.travis.yml

@@ -4,7 +4,8 @@ env:
     global:
         secure: "BB9eiRNXC1PfNRLEifc0yQQZnM25zqaWNGVWN+atzT+NkxhVKyVr8+DoyPYaa8tOKybuSZhVkKnIiCd8iGMe3v+WyuHKFuhdiwdnEQhxbBlUCb9dDLEexI+J8QiYwC8AW/t6H9LWVwSka0RI3GJujJ8HKIBzW45I/j+1NlUte8U="
 before_script:
-    - sudo apt-get install -qq libgmp-dev libmpfr-dev doxygen
+    - sudo apt-get install -qq libgmp-dev libmpfr-dev doxygen graphviz
+    - apt-get remove doxygen
     - wget http://www.flintlib.org/flint-2.4.3.tar.gz
     - tar -xzf flint-2.4.3.tar.gz
     - cd flint-2.4.3
@@ -12,6 +13,12 @@ before_script:
     - make
     - sudo make install
     - cd ..
+    - wget http://ftp.stack.nl/pub/users/dimitri/doxygen-1.8.7.src.tar.gz
+    - tar -xzf flint-2.4.3.tar.gz
+    - cd doxygen-1.8.7
+    - ./configure
+    - make
+    - sudo make install
 script:
     - make CC=clang
     - make doc