Various image links becomes broken when "path prefix" language negotiation is enabled.

It looks like when the path prefix language negotiation is enabled, and when viewing a language other than the default language, all relative image paths specified outside of the css stylesheets becomes broken.

The images links that become broken includes:
sites/all/modules/supernav/images/tool_contract.gif
sites/all/modules/supernav/images/tool_expand.gif
sites/all/modules/supernav/images/collapsed.gif
sites/all/modules/supernav/images/close-small.gif
+ all images on the help page.

Attached is the patch that fixes this particular issue.