Log Message:
mate-desktop: Update to 1.21.2:

### mate-desktop 1.21.2

  * Translations update
  * Add new setting to control XKB modifier latching

### mate-desktop 1.21.1

  * Translations update
  * interface: add key to enable/disable primary paste from middlemouse
  * mate-desktop-item: replace deprecated gdk_error_trap_push/pop
  * mate-rr-config: replace deprecated gdk_flush
  * mate-rr: replace deprecated Gdk functions
  * mate-bg-crossfade: replace deprecated gdk_error_trap_push/pop
  * mate-bg: replace deprecated gdk_error_trap_push/pop
  * fix distcheck
  * add mate-language apis

### mate-desktop 1.21.0

  * Translations update
  * drop ancient and unused acinclude.m4
  * Add toggle for synchronizing QT_SCALE_FACTOR to GDK_SCALE_FACTOR
  * Change default cursor-size to 24px
  * Support background fallback on HiDPI
* mate-rr-labeler: fix font-color for dark themes