A "0x" prefix suggest hexadecimal values, not decimal.

This adds the same touch gesture support for Windows as already added
for Unix. Note that it uses Windows gesture detection instead of our own
here though to give the user a familiar experience. Unfortunately that
means we lose the three finger tap.

This also raises the base requirements to Windows 7 as that's when
Windows got proper touch support.

Switch from using Core events to using X Input events for pointer
devices in order to differentiate between mouse events and touch events.

Because FLTK doesn't understand X Input 2, we intercept these events and
translate them to core events where possible.