Add support for nv21 video format as found on android

Note that the same code could be used for nv12
11 jobs for master in 12 minutes and 22 seconds
Status Job ID Name Coverage
  Test
passed #16949
clazy

00:01:22

passed #16950
qmllint

00:00:18

 
  Build
passed #16954
archlinux

00:01:11

passed #16953
debian-sid

00:01:17

passed #16952
neon-bionic

00:01:20

passed #16951
ubuntu-trusty

00:01:05

 
  Deploy
failed #16959
allowed to fail
android

00:00:01

failed #16955
allowed to fail
linux-appimage

00:01:10

passed #16958
allowed to fail
mac-osxcross

00:06:00

passed #16956
allowed to fail
windows-mxe

00:05:57

failed #16957
allowed to fail
android

00:00:01

 
Name Stage Failure
failed
android Deploy
Running with gitlab-runner 11.11.2 (ac2a293c)
on fiesta umZyLAru
Using Docker executor with image kdeorg/android-sdk ...
Pulling docker image kdeorg/android-sdk ...
ERROR: Job failed: Error response from daemon: pull access denied for kdeorg/android-sdk, repository does not exist or may require 'docker login' (executor_docker.go:175:1s)
failed
linux-appimage Deploy
 * KF5Notifications
* Qt5Widgets, Integration with QWidget based desktop styles
* Qt5Qml
* Qt5Core
* Qt5

-- Configuring incomplete, errors occurred!
See also "/builds/kde/kaidan/build/CMakeFiles/CMakeOutput.log".
ERROR: Job failed: exit code 1