Stop confusing people and retire COMPAT_LINUX and COMPAT_LINUX32 kernel
build options. Since we have 64-bit Linux emulation we can't build both
emulators into the kernel. And I don't think it matters, Linux emulation
depends on loadable modules (via rc).
Cut LINPROCFS and LINSYSFS for consistency.
I haven't removed opt_compat.h, maybe we should as there no any COMPAT
MFC after: 2 weeks