Add possibility to hide/disable "close tab" button

Imagine a scenario where you've got lots of files open in one window and the window is narrow. Tab widths get so small that when switching between them using mouse rapidly it's really easy to accidentally hit close button. Say you don't want to use keyboard shortcuts and left pane. An option to disable close tab button would be nice, as middle mouse button could be used for that purpose.

See http://www.twitpic.com/3w20rc/full