Please test: use /dev/mem instead of /dev/console for memory-mapping framebuffers in X11 on PowerPC

[Nathan Whitehorn]

I would appreciate any tests or comments on the following patch (which 
is working fine on my hardware). The goal is to move X drivers from 
using /dev/console to map device memory to using /dev/mem, as on x86 
systems. This makes it so that the kernel framebuffer driver does not 
have to allow mapping of all physical memory and can behave like an 
actual framebuffer driver and along the way fixes some highly dubious 
behaviors of the ppc_video module on FreeBSD. The patch to libpciaccess 
may also result in some performance improvement.

http://people.freebsd.org/~nwhitehorn/ppc-xorg-devmem.diff

Please let me know if there are any regressions or other issues.
-Nathan