put in extern "C" in case we build as c++

src/io_win.c

@@ -43,7 +43,13 @@
 #ifdef __MINGW32__
 /* this prototype is missing from the mingw headers so we must add it
 	or suffer linker errors. */
-WINHIDSDI BOOL WINAPI HidD_SetOutputReport(HANDLE, PVOID, ULONG);
+#	ifdef __cplusplus
+extern "C" {
+#	endif
+	WINHIDSDI BOOL WINAPI HidD_SetOutputReport(HANDLE, PVOID, ULONG);
+#	ifdef __cplusplus
+}
+#	endif
 #endif
 
 int wiiuse_find(struct wiimote_t** wm, int max_wiimotes, int timeout) {