suzerain: #3127 improve description

Had not commented on the bandedness and what was mapped to what.
Also, the banded notion was implicit.  Be more clear.

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@45396 0bd85f0b-c151-43b9-a1e9-27231104551f