travis-ci - disable Linux/gcc build

.travis.yml

@@ -19,16 +19,16 @@ dist: trusty
 
 matrix:
   include:
-    - os: linux
+    #- os: linux
-      name: Linux gcc-6
+    #  name: Linux gcc-6
-      env: >-
+    #  env: >-
-          CXX="ccache g++-6"
+    #      CXX="ccache g++-6"
-          CC="gcc-6"
+    #      CC="gcc-6"
-      addons:
+    #  addons:
-        postgresql: "9.5"
+    #    postgresql: "9.5"
-        apt:
+    #    apt:
-          sources: [ 'ubuntu-toolchain-r-test']
+    #      sources: [ 'ubuntu-toolchain-r-test']
-          packages: [ 'libstdc++-6-dev', 'g++-6', 'xutils-dev', 'postgresql-9.5-postgis-2.3' ]
+    #      packages: [ 'libstdc++-6-dev', 'g++-6', 'xutils-dev', 'postgresql-9.5-postgis-2.3' ]
     - os: linux
       name: Linux clang-3.9
       env: >-