The dump script was limited to the memory space below 0xa0000 because
the memory-mapped area of the framebuffer started above there, making
the GNU Debugger refuse to dump that memory. Now, the script has got a
workaround for that.
The memory which is given to the emulated system is also reduced to 64
megabytes with this commit as to not use half a gigabyte of disk space
per memory dump.