Log Message:
mate-sensors-applet: update to 1.21.1:

### mate-sensors-applet 1.21.1

    tx: sync with transifex
    disable deprecation warnings for distcheck
    Add NetBSD support.
    Use make functions for HELP_LINGUAS
    add help to transifex config

### mate-sensors-applet 1.21.0

  * Translations update
  * Fix copyright for plugin files
  * Add dummy plugin
  * UDisks2 plugin cleanup