changed some vars (e.g. v_rec) to struct. Corrected make_all_adjoint_sources for waveform misfit and made the other make_all_adjoint_sources into make_tt_adjoint_sources (at some point I'll have to merge them again). Added a catch to make sure that, when running the program, one doesn't have more BIG variables (such as u_forward) in memory than strictly necessary.