Added -[gtm_runUpToNSeconds:context:] to GTMFoundationUnitTestingUtilities.
Many people were using -[gtm_runUpToSixtySecondsWithContext:] which was fine
until you started to see multiple failures in a single build and it could take a
long time for a test pass to complete. 60 seconds is often much longer than
necessary to know that a failure condition has occurred.

DELTA=15  (15 added, 0 deleted, 0 changed)

git-svn-id: http://google-toolbox-for-mac.googlecode.com/svn/trunk@613 7dc7ac4e-7543-0410-b95c-c1676fc8e2a3