[Piglit] [00/16] Enable concurrency for a lot of tests

[Marek Olšák]

This series enables concurrency for about one half of non-concurrent tests. The time it takes to run all of quick.tests improved from 14.5 minutes to 11.7 minutes on my Core i5 quad-core.

The tests which examine a specific behavior of the window framebuffer are not changed, because concurrency requires that a test is able to run entirely in a FBO mode (the -fbo parameter).

If all glean tests were converted to the piglit framework and the remaining non-concurrent tests were made concurrent too, I think I should be able to get to approximately 7.6 minutes per quick.tests run.

Marek