longjmp

! Fixed.
Ruby from C, exceptions

+ Ruby functions from prime.rb may now be called from stdlibc functions
  such as fopen() (in turn handling file includes etc.).
+ Exceptions no longer just kill the program without messages, but
  rather print an exception screen.
Exception

+ In theory, would now output an exception backtrace. In practice, mruby
  doesn't seem to generate one.
Library, mruby target

- Kernel library may be much shorter with -DDISABLE_STDIO and
  -DDISABLE_TIME
* Changed mruby target from µxoµcota to emerald
load

+ Additional files may now be loaded via "load". These files have to be
  single multiboot modules for now, but will probably be included in one
  large tar archive later.