Cleaning up code, and separating a little to allow native code to share

Cleaning up code, and separating a little to allow native code to share

> Split vfs/open.c into handle.c, allowing the handle code to be
  replaced in the native emulation code.
> Changed a few referenes to Uint to tVAddr

These changes were made to allow the kernel to be compiled as a
user mode executable for windows/linux, to improve turnover speed
for user applications.