vsprintf about done

The vsprintf function is now working well enough, according to my
tests it should do what the spec in vsprintf.h says.. Feel free to
test! :)
kprintf

Now, the kernel has its own printf function, based on the vsprintf
specified in lib/vsprintf.h. It writes to the screen using kputs(),
so it will work without any filesystem, since we are just writing
to the VGA memory address.