Blender Git Loki

Fix T38381, Fix T38184: key events getting lost when modal operator is running.

There is a hack for modal keymaps and double click events, which was (ab)using
the wmEvent.prevval variable to temporarily assign it KM_DBL_CLICK indicating
that the double click event was disabled. However the value of prevval can
actually be KM_DBL_CLICK in other circumstances too, which caused a key press
event to get converted to a double click event.