In debug mode, `urls` produces backslashes on windows

[PaulUithol]

The change in 6fdcd87 (see #233) seems to cause query_url_mapping (and thus Bundle.urls) to produce urls containing backslashes on windows.

Example:

I'm calling urls on a bundle containing an item js/lib/jquery-2.0.3.js. The mapping points to /static/. This will call resolve_source_to_url with filepath=u'D:\\<project>\\static\\js/lib/jquery-2.0.3.js' and item=u'js/lib/jquery-2.0.3.js'. In query_url_mapping, this will cause the needle to be u'D:\\<project>\\static\\js\\lib\\jquery-2.0.3.js', which will cause it to return a url of u'/static/js\\lib\\jquery-2.0.3.js'.

Which will obviously lead to a 404 when attempting to load this url.

[miracle2k]

While there may be other instances of Windows paths not being handled right, this particular one seems isolated to query_url_mapping, which is supposed to convert a filesystem path to a url, and as such by necessity will have backslashes in the input and needs to make sure to have backslashes in the output.

[czhang03]

It has been 3 years, is there any progress on this one?