Implement initialization of basic Firm types (such as primitive int) in FirmInterface

[maxvogel]

We do have implemented the following functions:

ir_mode* getIntegerMode();
ir_mode* getBooleanMode();
ir_mode* getReferenceMode();
ir_mode* getMode(shptr<ast::Type> ast_type);
ir_type* getType(shptr<ast::Type> ast_type);

For the implementation, check this.

If this is what you meant, please close the issue.