Media Overlays highlighting, custom styles from reader / user. fixed minor SMIL parsing issue
ah, reader method was missing (lost in recent merge? not sure...)
MO element visibility cleaned-up (optimised, by using first 100% visible item, of previous partially-visible item)
fixed minor MO bug: playback status was out of sync in edge-case of embedded video/audio sync
Merge commit 9a2e69fb821bcf96ca948764d86c98061b4ffa11 of branch 'develop' into txtr_dev