Calling python print in a thread can segv vim.
Improve filtering: from 0.027s to 0.021s
Use get() to retrieve the translation unit.

While I cannot show any performance improvement, I'll argue that the
complexity of retrieving a translation unit is now two times faster.

The python "in" keyword has to walk to the datastructure once, and we
walk a second time to retrieve it. We only walk it once now.
Merge branch 'perf'

Conflicts:
	plugin/libclang.py