Move IOFile to a separate file

Reduces the number of files that need to be recompiled
when making changes to FileUtil.h.

Source/Core/Core/State.cpp

@@ -13,6 +13,7 @@
 #include "Common/ChunkFile.h"
 #include "Common/CommonTypes.h"
 #include "Common/Event.h"
+#include "Common/File.h"
 #include "Common/FileUtil.h"
 #include "Common/MsgHandler.h"
 #include "Common/ScopeGuard.h"