up to doom:

- Return from pedicel_main() normally (to idle)

** Checkpoint: ring0 process working

- VFS layer (open/read/write/...) with USTar filesystem (for initrd)

** Checkpoint: files not linked to but accessible by the kernel

- Ring3 memory mappings 
- Ring3 privilege switch

** Checkpoint: welcome to userland

- Syscall interface
- Implement syscalls needed for doom

** Checkpoint: can run simple programs, ring 3, loaded from filesystem 

- Properly handle the keyboard interrupt (keyboard buffer)
- Port DOOMgeneric (few functions with Framebuffer/ticks/etc.)

** Achievement: It runs doom!