Added syntax error for malformed #pragma cyclus directives

This adds a filter that causes the preprocessor to fail in the event of a syntax error on `#prama cyclus` directives. This prevents odd compile time and runtime failures from these pragmas being skipped by cpp and cycpp. See [this thread](https://groups.google.com/d/topic/cyclus-dev/JlG1pMYxnoI/discussion) for an example.