der: tag ordering doesn't follow X.680

[tarcieri]

The DerOrd of tags is not correctly implemented per the rules of X.680:

8.6 The canonical order for tags is based on the outermost tag of each type and is defined as follows:
a) those elements or alternatives with universal class tags shall appear first, followed by those with
application class tags, followed by those with context-specific tags, followed by those with private class
tags;
b) within each class of tags, the elements or alternatives shall appear in ascending order of their tag numbers