BUG: adding test for vnl_sparse_matrix::mult()

Change-Id: I70e9df2669172f6cd96bd1615e397fad26208c5a
BUG: size of q buffer should actually be (this->rows())*pcols.

Change-Id: I6dc354623338fa0bd787255fab5ac635b99669d3
Merge topic 'fix-vnl-sparse-multiply-dense'

d503f03e BUG: size of q buffer should actually be (this->rows())*pcols.
aa31d323 BUG: adding test for vnl_sparse_matrix::mult()