Basic Storm:
- Slight overall performance improvement due to how the standard delimiter rules are written.
- Fixed an ambiguity in the grammar regarding true/false. Discovered during development of a new parser.
- Better error message when attempting to use a key for an iterator type that does not supply keys.

Progvis (0.6.9):
- Allow using `#define X n` to define simple integer numeric constants. This is to make it possible to define
  symbolic array sizes that work in both C and Progvis.
- Fixed a few bugs after the re-structuring of the internals in the C frontend.
- Fixed a crash when using custom types in arrays.
- Progvis now better highlights memory accessed by the C standard library (e.g. `strlen`, `strdup`).