clang bindings: update to da6a6f087b

da6a6f0 [libclang/python] Add a few "cursor kinds" that were missing in the python
        binding for libclang.
c965f76 libclang: add a function to check whether a member function is pure virtual
52bb2a0 Fix return type of isBitfield in the binding definition
411d33a [libclang] Expose record layout info via new libclang functions:
11d6cd3 cindex.py: Handle NULL pointers when parsing translation units
bba99ad [cindex.py]: Use spaces instead of tabs
69a8552 [cindex.py] Add cache for CompletionChunk spellings
eca36d1 [cindex.py] Replace CachedProperty with our own implementation
e43d386 [cindex.py]: Speed up lookup of the completion kind
d829379 [python bindings] Expose cursor.referenced (clang_getCursorReferenced).
379ffe4 Fix a copypasto bug. Also rename the parameter in question to not
        shadow the 'file' builtin, and fix up a docstring a little.
b03b57d [clang.py] Add Cursor.get_arguments()
6988666 Python bindings: fix typo.
724d0dc Python bindings: Add missing availability kind.