Major mode to edit GNU Smalltalk code (http://smalltalk.gnu.org/)
and interact with an inferior GST interactive session.

Provides the usual functionality:
- Keyword highlighting.
- Automatic indentation.
- Syntax-aware navigation.
- Code templates.
- Interacting with an Smalltalk REPL from within the source code.
- Support for prettify-symbols-mode.
- defun navigation.