removed some unnecessary shared_ptr #81

[blackbird806]

For the SDL_Semaphore going back to raw C style is what seemed the most straightforward for me, using unique ptr with custom deleter feels overkill since it's only destroyed at one place.

[Macdu]

Nice (although I'm not sure whether I would prefer to use a reference instead of a pointer for mz_zip_archive).
For the semaphore stuff, what the code is doing right now is

• Thread 1 allocates ThreadParams on its stack then starts Thread 2
• Thread 2 copies ThreadParams to it stack then notifies Thread 1 using a semaphore
• Thread now can now return, making the inital ThreadParams invalid

This is really overcomplicated for nothing, it would be a lot easier to just do:

• Thread 1 allocates ThreadParams on the heap using new, starts Thread 2 and return
• Thread 2 reads ThreadParams then delete it using delete
  No more need for a semaphore.