Update CI matrix with gcc 5 & 8

.ci/install.sh

@@ -22,7 +22,7 @@ if [ $TRAVIS_OS_NAME == linux ]; then
         -o libsodium-${LIBSODIUM_VERSION}.tar.gz
     tar xfz libsodium-${LIBSODIUM_VERSION}.tar.gz
     pushd libsodium-${LIBSODIUM_VERSION}/
-    ./configure && make && make check && make install         
+    ./configure && make && make check && sudo make install         
     popd
     popd
 

.travis.yml

@@ -22,8 +22,23 @@ matrix:
     - os: linux
       compiler: gcc
       env:
-        - CXX_VERSION=g++-6
-        - CC_VERSION=gcc-6
+        - CXX_VERSION=g++-5
+        - CC_VERSION=gcc-5
+        - TESTS=ON
+        - USE_BUNDLED_BOOST=ON
+        - LIBSODIUM_VERSION=1.0.16
+      addons:
+        apt:
+          sources:
+            - "ubuntu-toolchain-r-test"
+          packages:
+            - "g++-5"
+            - "lcov"
+    - os: linux
+      compiler: gcc
+      env:
+        - CXX_VERSION=g++-8
+        - CC_VERSION=gcc-8
         - TESTS=ON
         - COVERAGE=ON
         - USE_BUNDLED_BOOST=ON
@@ -33,7 +48,7 @@ matrix:
           sources:
             - "ubuntu-toolchain-r-test"
           packages:
-            - "g++-6"
+            - "g++-8"
             - "lcov"
     - os: linux
       compiler: clang
@@ -51,7 +66,6 @@ matrix:
           packages:
             - "clang++-6.0"
             - "clang-6.0"
-            - "g++-7"
 
 install:
   - ./.ci/install.sh