- PS/2 answers with ERROR if PS/2 mouse is not connected,
  read_ack should handle error cases correctly. We should
  also probe correctly for the mouse. (0xFE on all commands)
- bochs shows us distorted text console output, why?
- bootloader has trouble detecting drive geometry of hard disks,
  only the floppy mode works reliably at the moment (in emulators
  and on real machines). Especially USB-pens in floppy BIOS emulation
  seems to report wrong CHS values.
- GUI: sort out a readable and type-safe (as much as possible)
  modus operandi. Accesses via base member chains are type safe, but
  we have to know the depth of the hierarchy of a derived class. Casts
  on the other hand are shorter to read, but not type-safe.
- real hardware like the Asus EEEPC 701 cannot switch A20 correctly,
  no clue why?
- if a task ends, what should we do? currently we crash
- libc is too closely coupled to kernel code; the initializers,
  calling the kernel_panic function, etc. We must decouple with
  a special module providing the global variables (from the point
  of view of libc, like the console or the memory manager). The
  kernel_panic function should be a callback hook we provide from
  outside of the library. Then in the libc test directory we have
  to implement a stub module for instance using some host functions
  like standard io of the host C library
- VGA graphic mode switch fails with optimizations on (at least with
  gcc and clang)