Tests are very brittle on low memory cards

```
I'm working with a 1Gb card (Quadro FX 3800, if it matters) and the test
suite fails (cuda_malloc, unsurprisingly) when I attempt to run it as it's
currently checked in on HEAD. RayleighTiming, at least, fails, as it
defaults to trying a 384^2 x 192 grid, which I can't allocate. Easily fixed
by modifying the test, but I think that the test should probably run
unmodified on any reasonable card.

One simple change I can see would be querying the card for available memory,
and then running each test at a resolution that fills most of the available
memory (up to some maximum.) If you are amenable to this change, I'm happy
to make it for you, in fact.

```

Original issue reported on code.google.com by `andrewhh...@gmail.com` on 13 May 2010 at 10:01