dtrmv_ltu parallelization

[tengjiang]

3 parallelization methods:

• with OpenMP barrier #pragma omp barrier, partially sync the progress of each CPU and save the intermediate result in a temporary local f64 variable
• Block-wise partitioning with a temp vector. Also parallelize dcopy.
• Cyclic partitioning with a temp vector. Also parallelize dcopy.

Modified the test file for design space exploration.