If a monitor's max resolution is a portrait resolution, then assume it is
a native portrait monitor and add portrait versions of the common modes.
https://bugzilla.gnome.org/show_bug.cgi?id=782294
Move code dealing with MetaOutputKms and related functionality to its
own file. Eventually, MetaOutputKms should become a GObject based on
MetaOutput, and this commit is in preparation for that.
https://bugzilla.gnome.org/show_bug.cgi?id=785381
Some output devices only advertise their preferred mode even though
they're able to display others too. This means we can include some
common modes in each output's supported list.
This is particularly important for mirroring, since we can only mirror
outputs which are using the same resolution.
https://bugzilla.gnome.org/show_bug.cgi?id=744544
