TRAVIS: try to fix travis build

.travis.yml

@@ -1,6 +1,13 @@
 language: c
 compiler: clang
 before_script:
-    - sudo apt-get install -qq libflint-dev
+    - sudo apt-get install -qq libgmp-dev libmpfr-dev
+    - mkdir flint
+    - wget http://www.flintlib.org/flint-2.4.3.tar.gz
+    - tar -xzf flint-2.4.3.tar.gz
+    - cd flint-2.4.3
+    - ./configure --prefix=/usr --with-gmp=/usr --with-mpfr=/usr CC=gcc CXX=g++
+    - make
+    - make install
 script:
     - make