COO OpenCL: Removed assert() in SpMV.

The code for this was fixed/added already here:
deae066e246de8f7931857ddfe9be4f916eb71f9
libviennacl: Fixed compilation problems with CUDA and unified integer type.

Instead of a plain 'int', the ViennaCLInt typedef is now used.
SpMdM: Added implementation for coordinate_matrix.

CPU version was already prepared. Added OpenCL and CUDA implementation.
This commit fixes also fixes recent problems of coordinate_matrix-times-vector for CUDA.