* additional interaction enhancements

* additional interaction enhancements
    - intf_UserFatal takes an addition bool-argument now to set whether the error message will be blocking in the interface or not (so TRUE = blocking)
    - intf_UserWarn is always non-blocking and is used to check important, localised warnings to the user
* wx: a compilation fix, but no update to the current API
* osx: complete implementation of the interaction framework using some Carbon (!) functions, because the needed icons aren't accessible through Cocoa. Regrettably, I had to add yet another nib-file to keep the code clean and readable.

The Error-dialogue is no longer re-usable (so the specific ID was removed). The interface needs to keep track of the reported errors and warnings. Thus, it may discard them as requested by the user and doesn't need to care about the core.