Hi All

When I was trying to open a core of an overflow stack panic result, the bt command caused a segment fault, after a while I figured out the overflow stack is not supported by crash utility.

This patch is trying to initialize the overflow stack information on startup stage, and the bt command works as expected to dump the correct call trace in the overflow stack, currently  it only apply to arm64 target.

I'm not sure if any other sub command also need to be fixed for full support for the overflow stack, please advise and I'll try to improve the patch.