* exceptions.cc (signal_exit): Kill any executing child process if we're dying.

* exceptions.cc (signal_exit): Kill any executing child process if we're dying.
* path.h: Remove unneeded extern.
* spawn.cc (std_suffixes): Make static.  Don't set dwProcessId here since it
makes the process unsignalable.  Set strace flag that this is an execed process
stub.
* strace.cc (strace::vsprntf): Use strace flag to indicate when to visually
flag that this is an exec stub.
* include/sys/strace.h (strace): Add 'execing' flag.