trilinos: add Python bindings

* add `--with-python` flag to build PyTrilinos bindings.
* patch `packages/PyTrilinos/src/CMakeLists.txt` and
  `packages/Sundance/python/src/CMakeLists.txt` to enable Clang to
  link properly.
* upgrade to Trilinos 11.2.3 to correct syntax errors in EpetraExt
  (see https://gist.github.com/guyer/5796687).