Merge pull request #214 in CASA/casa6 from CAS-10894 to master
* commit '0e2f709d2ba658f835b57b76b56ab53a733ffc2f':
updated codes based on comments by Takeshi and Renaud.
remove the lines to set/restore OMP_NUM_THREADS.
update the casa6 code and cleaned the casa5 code
update lines to set/restore OMP_NUM_THREADS.
update do_weight_mask() and set OMP_NUM_THREADS as 1.