Overlapping symbol ranges cause some annotations to draw below correct depth

[sorghumking]

A symbol's annotation text should appear at the vertical center of the symbol's range. However, annotation text for a symbol X within the range of a symbol Y will draw below Y's annotation text instead of drawing at symbol X's vertical center.

For example, in the diagram below, both the Rootlet and Oolite annotation text incorrectly draws below the text of the large Planar symbol ("Planar range").

[sorghumking]

Fixed by 3e243d1...