[GSoC Weekly Status #2] bhyve debug server enhancements

Hello,

I've spent most of this week testing and polishing the VM single-step
functionality for AMD hosts.
Since this functionality relies on the RFLAGS.TF bit, I've settled for a
less complex approach that intercepts and restarts any instructions that
may modify the RFLAGS register (popf/pushf) while making sure that the
guest executes correctly. Most of the testing consisted of stepping through
various interrupts which use popf/pushf.

I also managed to get a head start on implementing hardware watchpoint
support for bhyve's gdb stub [1].

Bojan

[1] https://github.com/bnovkov/freebsd-src/tree/bhyve_watch