Auto merge of #572 - malbarbo:android-x86_64, r=alexcrichton

Add x86_64-linux-android support

When rust add support for x86_64-linux-android, the tests may be run with:
`rustup target add x86_64-linux-android && bash ci/run-docker.sh x86_64-linux-android`.

Android x86_64 emulator does not work without hardware acceleration, so we are not able to run tests on travis.