evdev instead of ExplorerPS/2

[MadMan2k]

I think it would be better to use evdev in the cases where ExplorerPS/2 
is used right now,
because ExplorerPS/2 is insufficient for new mice.
For example pressing the scrollbutton(button 4) on a MX510 is sending 
button 6(back-button) on release
also the window switcher(button 8) is not supported.

Since the MX5?? series are quite popular this fix should probably get 
some attention.

M2k