Improve the code generation even more ...

[chrisdutz]

Currently we are planning on adding support for:

• "state" fields, that allow to explicitly store parser arguments as fields.
• "constants" types, that contain a collection of const fields which produce a lot more lightweight Constants types
• "globals" types, that will contain global information which is available everywhere in the parser
• "context" types, that will contain information which is availalbe everywhere in the parser but is related to one particular message