Fix for caption text height [Delivers #81023116]
Constant for magic number
Merge branch 'feature/hls-subtitles2' of https://github.com/jwplayer/jwplayer into feature/hls-subtitles2

# By Charles Dietrich (2) and Rob Walch (2)
# Via Rob Walch
* 'feature/hls-subtitles2' of https://github.com/jwplayer/jwplayer:
  renderer cleanup
  event class cleanup
  Constant for magic number
  Fix for caption text height [Delivers #81023116]