Enable AVX2 at runtime on Travis-CI and AppVeyor#963

Merged

rouault merged 3 commits intouclouvain:masterfrom rouault:travis_avx2

Jul 1, 2017

+187-2

Commits on Jul 1, 2017

.travis.yml: try to run tests in -mavx2 mode if the CPU supports it
rouault
committed
appveyor.yml: add a /arch:AVX2 config on Windows
rouault
committed
Add tools/travis-ci/knownfailures-Ubuntu14.04-clang3.8.0-x86_64-Release-3rdP.txt (copied from knownfailures-Ubuntu12.04-clang3.9.0-x86_64-Release-3rdP.txt)
rouault
committed