Added the command "j6tw <pml4> <addr>" which takes any arguments that
evaluate to addresses or integers. It displays the full breakdown of the
page table walk for the given address, with flags.
Improve the j6stack command in two ways: first, swap the order of the
arguments, as depth is much more likely to be changed. Second, on any
exception accessing memory in the stack, print the exception and
continue instead of failing the whole command.
GDB works far better now with QEMU's `-S` flag. No longer does it
complain about changing the target from 32 to 64 bits. Get rid of the
old `waiting` loop and `sleep` call in the GDB config for the kernel.
Tags: debugging
