Add scratchpad handler

* Currently the BIOS tries to write something to scratchpad and it fails
because its address is not our currently supported range. So add a new buffer
for the 16KB scratchpad used by the CPU and add a function to use it if the
address is in the correct range.

* Also shorten some function names and change some array to C-style because we
like to work with pointers and STL doesn't like that.