[RFC] removed ffmpeg libraries from our dllloader

This PR is meant as rfc as its not completely done yet (needs some platform love and for windows mingw libs needs to be compiled before the vs project now).
On windows the libs are now loaded via their import library (other platforms needs to link now to the lib as well, hint, hint :). 
I've removed a bunch of critsections and I need some comments here if I deleted too much and we still need them at some places.
I moved the *_register_all() methods to application.cpp to call it only once on start. Probably there's a better place to call them and to prevent to pull their header in application.cpp?