Building with integration tests on Windows fails

[axeluhl]

The JarFileScanner gets confused with the platform-agnostic forward slashes used by JAR file entry names when the includes/excludes patterns are adapted to using the platform-specific File.separator. This way, the compile-with-coverage integration tests keeps failing on Windows.

As a side effect, it turns out that on slower / virtualized Windows environments the gwt-test-fail tests fails for a timeout that may be set too short. Increasing the default timeout from 60s to 600s may solve this, too.