[Emscripten] graphical glitches and other minor bugs

[Deleted user]

While testing the web version, I encountered some bugs:

• mouse scrolling directions are inverted
• tab selectors highlight the wrong label, working somehow like a togglebutton
• turbo-badger has the number in the slider line
• in the customized item list, under circumstances the item closing cross is drawn at the titlebar of the window

[rupertsteel]

Something more to add, the progress dialogue demo doesn't show a progress bar with the TurboBadger theme.