Genie:  Don't reset signal handlers for new thread

Since the signal handlers aren't unshared in this case, this affects the
calling thread as well, which is clearly wrong.
Genie:  Inline away Process::ResetSignalHandlers()
Genie, relix:  Move signal handlers to process
Merge branch 'signal-handlers'
Genie:  Fix always-unsharing of fs info and fd map