c4d350c260
Use feature options for things that are optional features, update the docs. Visible changes here is that the 'print-backends' option got renamed to 'print' to go better with 'media', and the 'tracker3' option got renamed to 'tracker'. For options that have been changed into features, the syntax now is -Dfeature=enabled or -Dfeature=disabled or -Dfeature=auto.