blocked back-transformation for the non-symmetric eigenvalue problem - Contribution...

blocked back-transformation for the non-symmetric eigenvalue problem - Contribution from Mark Gates (UTK)

From mark:
It blocks NB gemv calls into one gemm call inside trevc. To do that, it
needs a new routine, trevc3, because unfortunately the lwork was not
passed into trevc. (I highly recommend all new routines always pass
lwork and lrwork, where applicable, to enable future upgrades & to
catch lwork bugs.)