Modified calc_n_coarse_channels to support GBT and Parkes
Modified calc_n_coarse_channels to support GBT and Parkes

EE: Please check this does what you think it should.

Former-commit-id: c51574baaf17710ea42e7bc129328a3ce5fd5946
UCBerkeleySETI/blimpy,UCBerkeleySETI/blimpy