This patch adds a preference to reverse the mousewheel seeking; that is, scrollwheel up goes backward in the file and scrollwheel down goes forward in the file. This is in addition to the existing mousewheel media seeking preference.
My rationale for this is that in my mind, videos are like a web page or a document I'm viewing; if I want to go further down in the document, I scroll down. So if I want to go further "down" in a video, I scroll down.
Tested against svn r3010, built with Qt 4.5.1 on Linux.