combine parallel-do in qeq_initialize(), get_hsh(), get_gradient() in QEq

[KenichiNomura]

fork-joining every QEq loop will incur too much overhead. change the three $omp parallel-dos into one $omp parallel at the beginning of QEq and three $omp do for each function.

[kuangluvasuka]

Two functions, qeq_initialize() and get_gradient(), that are outside the DO loop (line 95) can be combined in a single parallel directive. There are two EXIT statements in the DO loop (line 111 and 112), but OMP doesn't allow EXIT or RETURN occur within a parallel directive.

[KenichiNomura]

Yes, that's a good point. Another limitation in OpenMP.. Since the multithreading comm and comp strategy seems not ready for production use according to the conversation with Nick, we would not ned to pursue this issue at this moment.