Fix incorrect file name.
Use OS X 10.8 SDK instead of latest SDK for stable regression test results.
Make tests less fragile.

Xcode stores intermediate files in directories with randomized names.  But
directory names aren't completely random, only suffix is random.  So I detect
this random part and check that it's the same for all files in Xcode project.
Prefer UTF-8 encoded non-ASCII characters to sequences like \u0308.

I think it is more readable.  If necessary, it's easy to add command-line
option to ensure ASCII in compile_commands.json.

This change breaks Python 3 compatibility.
Make compatible with Python 3 again.