compressed_matrix: Implemented CSR-adaptive in CUDA and OpenCL.

See paper "Efficient Sparse Matrix-Vector Multiplication on GPUs using the CSR Storage Format"
by Greathouse and Daga, presented at SC 2014.
CUDA: Fixed compilation error in triangular solve kernels.

Introduced by 0ba719f3ec0eb284f9e3d4faea9aadb77de0141a.