Add profiling for unit tests.
Add profiling for unit tests.

This adds a --with-profiling argument for our unit tests that writes a
reviewboard.profile file containing profile data on our test run. We can
make use of this to figure out where the slowdowns are in our test
suite.

1tush/reviewboard,chipx86/reviewboard,KnowNo/reviewboard,sgallagher/reviewboard,custode/reviewboard,bkochendorfer/reviewboard,1tush/reviewboard,1tush/reviewboard,1tush/reviewboard,reviewboard/reviewboard,sgallagher/reviewboard,custode/reviewboard,beol/reviewboard,chipx86/reviewboard,bkochendorfer/reviewboard,brennie/reviewboard,beol/reviewboard,KnowNo/reviewboard,1tush/reviewboard,brennie/reviewboard,1tush/reviewboard,brennie/reviewboard,davidt/reviewboard,1tush/reviewboard,custode/reviewboard,chipx86/reviewboard,beol/reviewboard,brennie/reviewboard,bkochendorfer/reviewboard,sgallagher/reviewboard,davidt/reviewboard,davidt/reviewboard,reviewboard/reviewboard,custode/reviewboard,beol/reviewboard,davidt/reviewboard,bkochendorfer/reviewboard,1tush/reviewboard,reviewboard/reviewboard,KnowNo/reviewboard,1tush/reviewboard,KnowNo/reviewboard,reviewboard/reviewboard,sgallagher/reviewboard,chipx86/reviewboard