suzerain: add channel QoI computations

These are based upon suzerain/bl.{h,c} but are
simpler since there's no edge finding requirement.

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42833 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: add Ma_tau

Coded this up for the new channel logic.
Simple enough to add it here as well.

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42834 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: rename "bl.wall" -> "bl.visc"

Making space to later dump wall quantities if we want them.

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42835 0bd85f0b-c151-43b9-a1e9-27231104551f