[C++] Drop GCC 5 from Travis.

Author: mjpt777

.travis.yml

@@ -92,23 +92,6 @@ matrix:
  script:
  - ./cppbuild/cppbuild
 
- # gcc-5
- - env: COMPILER=g++-5
- compiler: gcc
- os: linux
- addons:
- apt:
- packages:
- - g++-5
- - libsparsehash-dev
- sources:
- - ubuntu-toolchain-r-test
- before_script:
- - export CXX=$COMPILER
- - ./gradlew
- script:
- - ./cppbuild/cppbuild
-
  # gcc-6
  - env: COMPILER=g++-6
  compiler: gcc