suzerain: rework NRBC accumulate kernel signature

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@43785 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: add test_blasext_zgedsummv55

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@43786 0bd85f0b-c151-43b9-a1e9-27231104551f