atomic tests timing out on Windows

[Martin Sebor <se...@roguewave.com>]

Looks like the two atomic tests, atomic_add.exe and atomic_xchg.exe,
are timing out in some (optimized) MSVC builds on Windows.

First, the timeout seems to be set to 180 seconds on Windows but 300
seconds on all other platforms. I think we should increase it on
Windows to make it consistent. How do we go about adjusting the
timeout?

Second, I'm concerned that the atomic tests are timing out at all
because when they run to completion they only take about 15 to 20
seconds (depending on the hardware). Farid, have you seen this in
your manual builds? (The test are important because they exercise
functionality that string depends on for thread safety).

Here are a couple of builds with the timed-out tests:
http://people.apache.org/~sebor/stdcxx/results/win_xp-2-x86-msvc-32b-8.0-12d-win32-558871-log.gz.txt
http://people.apache.org/~sebor/stdcxx/results/win_xp-2-x86-msvc-7.1-12d-win32-558871-log.gz.txt

Martin