sysDef refactor, part 1 - PLEASE READ NOTE

THIS WILL NOT COMPILE!!!
i'm still working on it

to @cam900: DO NOT PULL TO YOUR ES5506 BRANCH YET - wait until I am done
with this refactor

to @grauw: DO NOT PULL TO YOUR OPL4 BRANCH YET - wait until I am done
with this refactor

src/engine/engine.cpp

@@ -2425,6 +2425,9 @@ bool DivEngine::deinitAudioBackend() {
 #endif
 
 bool DivEngine::init() {
+  // register systems
+  registerSystems();
+  
   // init config
 #ifdef _WIN32
   configPath=getWinConfigPath();