fix_mw: consistent mouse handling on all platforms

Make mouse wheel handling similar across platforms without requiring
window focusing.

This is achieved by replacing on Windows bindings to MouseWheel with
bindings to virtual events MWheel. These events are sent to the windows
with the mouse pointer instead of to the ones with focus.

Signed-off-by: Cristian Stoica <crististm@gmail.com>
allow board to take focus on click

Signed-off-by: Cristian Stoica <crististm@gmail.com>