Patch moves HandleSIGSEGV in HostFactory.cpp to a non-frontend host signal handler, then registers its own frontend signal handler to catch unhandled segfaults.
This requires implementing custom ASM dispatchers for the interpreter
side of things so it works correctly.
Allows all of our CPU backends to safely support signaling.
This is a bit of a nightmare change and requires rethinking logic about
debugging in some instances.