suzerain: use power not multiply

Minor hygiene thing.  Not so much necessary
as it differed from tilde_u and those expressions shouldn't
differ in form.

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@45405 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: fix error message

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@45406 0bd85f0b-c151-43b9-a1e9-27231104551f