Merged and pushed.

Yes, please! I looked at the patch and also like the fact that it fixes the
spelling of "God". :-)

The test worked on our Windows machine. Can I merge this?

Michael ran the test on his OS X machine and hill-climbing is correctly stopped 
after 2 seconds (thanks Michael). 

I will run the test on our Windows machine tomorrow.

Maybe Michael can help us out? Could you give me your bitbucket username (so I can give you access), clone 
the repository linked below and run the following command, please?

./fast-downward.py ../benchmarks/sokoban-opt11-strips/p10.pddl --search "astar(ipdb(max_time=2))"

Hill-climbing should abort after 2 seconds (for me on Linux the log says "iPDB: hill climbing time: 2.02s").

Off the tracker, Erez said he didn't have access to a Mac. I think we're using
an OS-specific API here, so I think we need a test on OS X. Any ideas whom to ask?

Erez, could you run Jendrik's test on OS X?

I think we have done neither functionality tests nor runtime tests on these 
platforms. I could do a small functionality test on Windows, would that be 
sufficient?

Have we ever tested ExactTimer on Windows and Mac OS?

Currently, the CountdownTimer uses the inaccurate Timer class. Since I need to use 
the CountdownTimer for exact measurements, I'd like to move this issue forward.

I have written a microbenchmark which showed that using clock_gettime() is faster 
than times():

Running times() 10000000 times: 1.54408 seconds
Running clock_gettime() 10000000 times: 1.46931 seconds

I have also prepared a pull request, which lets ExactTimer return its result in 
seconds rather than nanoseconds and renames ExactTimer to Timer:

https://bitbucket.org/jendrikseipp/downward/pull-requests/34

What do you think, Malte?

One caveat is the dependcy on librt, 
although I don't think that's a real 
issue.

We believe that ExactTimer only has advantages over Timer (higher precision while 
being similarly cheap to compute). This needs to be tested and if it is the case, 
the ExactTimer class should be used instead of the Timer class and should be 
renamed to Timer.