ungrab_pointer ungrab_pointer(+Time) ungrab_pointer(+Displayable, +Time)
Release the pointer and any queued events
if this client has it actively grabbed, unless the Time
specified is earlier that the last-pointer-grab time or
later than the current server time. It also generates
Displayable is the ProXL Displayable. If omitted, the default Display is used.
Time is a timestamp in milliseconds (from an event) or
current_time. If omitted,
current_time is used.