Added meson features for explicitly enabling or disabling the dependencies freetype and fontconfig such that they won't be used even if present on the system.
The meson option use_fontconfig was changed to fontconfig with these possible values:
* 'enabled' (equivalent to old use_fontconfig=true)
* 'auto' (equivalent to old use_fontconfig=false)
* 'disabled' (equivalent to old use_fontconfig=false AND report an error if fontconfig is required on this system).