GNU Make on Windows now appears to be working reliably. This change also
fixes a bug where, after fork the Windows thread handle wasn't reset and
that caused undefined behavior using SetThreadContext() with our signals
This change implements a new approach to function call logging, that's
based on the GCC flag: -fpatchable-function-entry. Read the commentary
in build/config.mk to learn how it works.
You can now use psapi.dll and pdh.dll. Some TODOs for Windows have been
cleared out. We might have a working load average for the platform that
should help GNU Make work well.
