support running tests in parallel

_From [derek.br...@gmail.com](https://code.google.com/u/117968039472581148324/) on April 08, 2009 11:07:09_

The latest CTest (will become 2.6.4) support running tests in parallel.
As part of getting the Windows runall tests working we should tweak them to
support parallel execution, which they do not today due to two factors:
- they all run the same apps (calc.exe, notepad.exe) and thus can trip over
each other's registry settings
- they use closewnd.c which closes an app with a certain name in its
title, which will close all instances of the app

My proposed solution is:
- make a copy of calc.exe or notepad.exe and name it with the test name
- have closewnd.c find the window and do a clean shutdown (as opposed
to drkill) using the pid instead of the name. this can be done by
using EnumWindows() to enumerate top-level windows and then using
GetWindowThreadProcessId() to find the one owned by the target pid.

_Original issue: http://code.google.com/p/dynamorio/issues/detail?id=111_