* Changes in 2.2.15 (Jun 1, 2021)

+ A new adapter, OnOffGraphic, is added.

+ MovieGraphic and AudioSound can change their playback position.

+ AnalogInputMonitor and WebcamMonitor can set the monitor position in
normalized units.

- A playback problem related with ComplementaryWindow is fixed.

- mlplayer can search stimuli in relative paths from the datafile location.

- The problem that mlhdf5 does not handle 64-bit intergers properly is fixed.
(Thanks to lucast4 from the NIMH forum)

- Fixed the ITI duration bug introduced in the previous release.