Comment 9 for bug 200601

Maybe we can use PR_FindFunctionSymbolAndLibrary or PR_FindSymbolAndLibrary and
lookup something GTK2.6 specific? I'm not sure what that would be though, but
here is a list of new symbols in GTK2.6: <http://www.gtk.org/api/2.6/gtk/ix05.html>.

Of course, this would require some C code as well as JS. In any case, I think we
should add a pref here:
'browser.tabs.mouseScrollChangesTab'
    0: Off.
    1: On.
    2: Behave according to platform.
Where 2 is default. If we don't add it here, we're sure to get an RFE for it
sooner or later anyway.

mconnor, think this could work? Where would we put the required C code for this?