python: make _decode_table_types aware of __int128

There are no ctypes types ready for int128. However, recognizing this
type and representing it as an array is better than simply erroring out.

* Add mapping between (unsigned) __128 C types declaration and ctypes
  parsing
* Add simple test case in test_clang to recognisze and use such types
* Fixes deprecation warnings about self.assertEquals in 2 other test
  cases.