Added decl_early_init() which is called when PLAYAGAIN is supported.

decl_early_init() is called when we are starting a game.  On first
start, it validates that global state is in the expected state.
When called on subsequent starts, it initializes global state to
expected state.

win/win32/winhack.c

@@ -97,6 +97,9 @@ WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine,
 
     win10_init();
 
+#ifdef PLAYAGAIN
+    decl_early_init();
+#endif
     sys_early_init();
 
     /* init applicatio structure */