add VirtualBox DRM driver

branches: 1.8.4; 1.8.6; 1.8.8;
remove the old drm sources.

you can now easily select trying external drm with "options DRM_EXTERNAL".

branches: 1.6.4; 1.6.8; 1.6.12;
support new drm.

XXX: not fully enabled yet. config(1) has a makeoptions bug
with complex conditionals. see files.drm / files.pcidrm for
some instructions on how to enable it.

remove some more local changes of the form "foo.h" -> <dev/*/foo.h>
by using makeoptions in files.drm/files.pcidrm. this reduces the
diffs against other drm code by about 40kb.

branches: 1.4.2;
Revert previous, i915drm works again.

- Use the extent manager to track mappings and provide sane offset
"cookies" for mmap. Now the radeon driver works on amd64!

- Use bus_dma for nearly all map types (carried over from prior patch).

- Plug some lock leaks in drm_bufs.c and remove superfluous locking in
drm_add_magic() (from git).

- Lower spl of mutexes to IPL_NONE (and so are now adaptive instead of
spin mutexes), save for irq_lock which is a spin mutex at IPL_VM.
Use mutex_spin_enter()/mutex_spin_exit() for irq_lock.

ok jmcneill@

branches: 1.2.2; 1.2.14; 1.2.34; 1.2.38; 1.2.40; 1.2.42;
Introduce options DRM_NO_AGP and DRM_NO_MTRR, so I can run this on
platforms that don't provide these services.

In drm_mmap, don't wrap the return value with atop() if we're on macppc.

While we're here, fix:
pci_intr_establish(&dev->pa.pa_pc, ...);
to:
pci_intr_establish(dev->pa.pa_pc, ...);

The former doesn't even compile on macppc, and I'm amazed that it works at
all anywhere else.

branches: 1.1.2;
Import DRM drivers, brought into shape by Yorick Hardy, posted to tech-x11.
Minor modifications by me:
-use an mi device major number
-(coarsly) divided into pci card specific and less specific parts, moved
the latter to dev/drm
-renamed autoconf attributes to reflect this
Todo:
-adapt all card frontends but i915 to drm include file location
-review the mtrr change
-make the change to agp_i810.c coexist with the fix for buggy VESA
BIOSes which is commented out temporarily
-RCS IDs etc style stuff
-LKM support (rescan support for vga)
-test