suzerain: memset in (rho, rho_E) submatrix

Less efficient, but I either need to use memset or to reach
down into the assembled matrix

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@43984 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: scale buf for (rho, rho_u)

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@43985 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: use buf for (rho, rho_w)

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@43986 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: use buf for (rho, rho_v)

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@43987 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: use buf for (rho, rho)

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@43988 0bd85f0b-c151-43b9-a1e9-27231104551f