drm/radeon: Handle -fms-extensions better (fixes the clang build).

FreeBSD has since switched to only using it for GCC (which apparently
complains about anonymous unions). In clang, it will enable Microsoft's
__wchar_t type, which (as in FreeBSD) conflicts with our own one.

We actually only need it for gcc44. Our gcc47 builds radeon.ko fine
without it.
Add a upmap(4)/kpmap(4) manual page.

Submitted-by: Robin Hahling <robin.hahling@gw-computing.net>
mdoc.local: Add version 3.9 for .Dx

While here, also add 9.3 for .Fx
upmap.4: Add missing .El