Cleanup includes
Removes some unnecessary includes with the goal of not having any files in common depending on outside files.
There is still one issue left after this. gc_delay_line uses generic_dpram from genrams. The only user of gc_delay_line seems to be gc_moving_average. So my question is, does anything at all use gc_delay_line or gc_moving_average? If not, perhaps remove this. Otherwise, can we move them somewhere else?