vout_ios2: add support for touch events to control an on-screen interface

To avoid collisions with existing touch gesture recognizers, a double-tap is needed to trigger a left-click mouse event
demux: avi: don't ask for fix on non fastseekable

A better way would probably keep not asking and
seek and load index when 'slow' seekable.
demux: libavi: fix boundary setup

confusion: wanted min of max.