Wish: "Safe" window selection with both mice buttons

Wish: Make it possible to “safely” window select objects (i.e. picking objects with the initial press of the LMB will be temporarily disabled, only window crossing them is allowed) when holding down the left mouse button, followed by holding the right one and then dragging the mouse, in a similar fashion like holding the Alt key prior normal window selection of objects. Not only this will be help to avoid those annoying situations with directly picking objects (while the goal was to select those with windows selection only), but it will be also handy for the people who use 3Dconnexion devices that lack a dedicated Alt button.