The code in input_server was pretty much all set for this, but there was
no way to configure the extra buttons. Add them to the mouse view in
Input preferences (up to 5 buttons are handled now)
Define a new B_MOUSE_BUTTON(n) macro to generate the bitmask for a given
button (numbered from 1).
Change-Id: I9091082277937d89b08464ff474e7bbb5db82401
Reviewed-on: https://review.haiku-os.org/c/haiku/+/180
Reviewed-by: waddlesplash <waddlesplash@gmail.com>
5bbf7f1be0