* Revert "Revert "travis: Test mbedtls too""
This reverts commit c4c60eac5ca756333034b07dd9e0b97741493ed3.
* travis: Build mbedtls from source on Travis
Use TOOLCHAIN_OPTION when calling cmake on mbedtls
* tests: only run DSA tests for non-mbedtls
crypto backends
This introduces a test suite for libssh2. It runs OpenSSH in a Docker
container because that works well on Windows (via docker-machine) as
well as Linux. Presumably it works on Mac too with docker-machine, but
I've not tested that.
Because the test suite is docker-machine aware, you can also run it
against a cloud provider, for more realistic network testing, by setting
your cloud provider as your active docker machine. The Appveyor CI setup
in this commit does that because Appveyor doesn't support docker
locally.
