ensure we use upgraded gcc as well as g++

.travis.yml

@@ -9,7 +9,7 @@ matrix:
         apt:
           packages: [ 'protobuf-compiler', 'libprotobuf-dev' ]
     - os: linux
-      env: COVERAGE=gcov-4.9 CXX=g++-4.9
+      env: COVERAGE=gcov-4.9 CXX=g++-4.9 CC=gcc-4.9
       addons:
         apt:
           sources: ['ubuntu-toolchain-r-test']
@@ -30,7 +30,6 @@ script:
  - echo '{"type":"Feature","properties":{},"geometry":{"type":"Point","coordinates":[0,0]}}' > test.json
  - ./tippecanoe -o test.mbtiles test.json
  - if [ -n "${COVERAGE}" ]; then
-       rm vector_tile.pb.o;
        ${COVERAGE} -lp *.o;
        pip install --user cpp-coveralls;
        ~/.local/bin/coveralls --no-gcov -i ./;