* Fixed an annoying bug which occured because of stack trampling due to
  the way I had written saveContextAndCallPull().
  * There is still some bug which manifests only in Bochs and Sun Virtual
    Box, where the active thread stops being pulled. It doesn't occur
    on real hardware, and is most likely data-structure related.

* Implemented support code for the x86 debug register debugger features.
  Can now use read and write breakpoints, and code-execution breakpoints in
  the kernel.
  * Implemented exception handlers for x86-32 exceptions 1 and 3 (debug
    and breakpoint exceptions).