Fix single star into double star

[klauspost]

Single star into double star did not work as expected.

Pattern a/b/*/e.f/** would not match a/b/c/e.f/g since the top level glob would be performed on a path ending with a /. Using filepath.Join(match, glob) will remove the trailing slash.

Two tests included for regression tests. And as a side bonus tests will now also pass on Windows.