Human readable format modifiers

This series adds support to display format modifier tokens in a human readable form, and expose a way to deliver that information to users up the stack. A static table holds that information, with the possibility of adding customized/specialized version to un-pack more complex forms of/for the format modifier (AMD or ARM FBC for instance). Even so, there are some examples in that table that show that is possible to combine/pack even complex representation of the format modifier, straight in.

libdrm seems a more natural place to have this in rather that up the stack in order to minimize some potential delta that might arise, but not also between kernel uapi and user-space, but also between different tools, so unifying it in libdrm seems the most appropriate.

It first syncs up with drm-next to catch up with the latest changes in drm_fourcc header (including adding new vendors and format modifiers).

The immediate user of this is modetest which was modified to make use of this change.

PS: I have a small follow-up for drm-next to let users modifying kernel uapi drm_fourcc header that they should also sync up w/ this table when new vendors, or format modifier token have been added. Will post a link to that once I git-mail that up.