nitcc: better name of generated classes to avoid name conflicts

Signed-off-by: Jean Privat <jean@pryen.org>
nitcc: remove 'print' in parser error

Information is available in the NError
object.

Signed-off-by: Jean Privat <jean@pryen.org>
nitcc: update tests with new syntax errors

Signed-off-by: Jean Privat <jean@pryen.org>