audit take_semaphore() usage, potential DryOS API change

[reticulatedpines]

I think critix might have spotted this. Here's my comment from dual_iso.c:

    // SJE TODO gain better understanding of why modern digic cams,
    // apparently including 1300D, fail to take the sem if 2nd param is 0.
    // On prior cams, 0 works fine.  But there are other uses with 0 on D678
    // that seem okay!  E.g. the menu sem.
    take_semaphore(isoless_sem, 1);

isoless_sem is one we make ourselves, so I'd guess this is an API change on Canon's side.

We should audit all our uses of take_semaphore() and see if the problem happens elsewhere. Potentially this could break a lot of things.