Travis-CI : Attempt to remove manual building from source of SDL2

Signed-off-by: Gabriel Ravier <gabravier@gmail.com>

.travis.yml

@@ -109,16 +109,6 @@ install:
     # Install required libraries
     - mkdir travisLibs && cd travisLibs
 
-    # Install modern SDL2
-    - SDL2_VERSION=2.0.10
-    - |
-      travis_retry curl -L https://www.libsdl.org/release/SDL2-${SDL2_VERSION}.tar.gz | tar xz
-      cd SDL2-${SDL2_VERSION}
-      ./configure
-      make -j ${JOBS}
-      sudo make install -j ${JOBS}
-      cd ..
-
     # Finished installing required libraries
     - cd ..