The ability of the clang rewriter to extract the type information for
some types of structs, unions, and pointers to the aforementioned was
somewhat buggy. This became exposed in a test_clang case after a user
upgraded to a newer kernel, wherein the struct definition changed. The
functionality in question is only used to pass json-ified representation
of the struct to python in order to program the Key/Leaf metaclass.

Improve support for this and other types, including unions.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>