Move rewindsave and dorewind declaration to a proper header instead of using extern.

desmume/src/saves.h

@@ -66,4 +66,7 @@ bool savestate_save (const char *file_name);
 void savestate_slot(int num);
 void loadstate_slot(int num);
 
+void dorewind();
+void rewindsave();
+
 #endif

desmume/src/windows/main.cpp

@@ -1071,9 +1071,7 @@ DWORD WINAPI run()
 			}
 			DRV_AviVideoUpdate((u16*)GPU_screen);
 
-			extern void rewindsave();
 			extern bool rewinding;
-			extern void dorewind();
 
 			if (staterewindingenabled) {