* travis: use newer 10.15 VM with newer xcode
* travis: fix macOS 10.13 build
* vo_sixel: don't leak the frame reference
* vo_tct: don't leak the frame reference
* vo_tct: remove unused variable
* player: allow vo to be switched at runtime
* demux: add function to refresh a track without (de-)selecting it
* vo_sixel: use draw_frame instead of draw_image
* vo_sixel: skip testdither init in fixed palette
* vo_sixel: Update libsixel constant values
* matroska.py: remove python2 support
* bootstrap.py: remove all python2 support
* vo_sixel: change default dither to "auto"
* vo_sixel: fix the image corruption with mlterm
* vo_sixel: support --vo-sixel-exit-clear[=yes]
* terminal: process input when foregrounded
OBS-URL: https://build.opensuse.org/package/show/multimedia:apps/mpv?expand=0&rev=250
