Revert "g++"

This reverts commit 6812e9b7.

.travis.yml

@@ -9,11 +9,7 @@ addons:
   ssh_known_hosts:
   - github.com
   apt:
-    sources:
-      - ubuntu-toolchain-r-test
     packages:
-      - gcc-6
-      - g++-6
     - libfreetype6-dev
     - libevent-dev
     - libsqlite3-dev
@@ -25,7 +21,6 @@ env:
 - USE_IRRKLANG=1
 before_install:
 - git submodule update --init --recursive
-- if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then sudo ln -s /usr/bin/gcc-6 /usr/local/bin/gcc; sudo ln -s /usr/bin/g++-6 /usr/local/bin/g++; fi
 - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then
     brew update > /dev/null;
     brew install freetype libevent sqlite p7zip dylibbundler > /dev/null;