[bug 977270] Don't infer platform if products don't match

If you're writing up feedback for Firefox for Android using Firefox, we
shouldn't infer the product from the user agent because it'd be wrong.
For example, you'd get something like Firefox for Android feedback with a
platform of Windows... wat?!
Update dennis to v0.4.2

v0.4.1 had a bug where it was throwing errors and not printing anything
to stdout and thus nothing gets into postatus.txt.

v0.4.2 fixes that.