Makefile.mingw corrections and made the code pass much stricter checks (now mandated by Makefile.mignw) to ensure GCC 14 readiness.

src/include/86box/snd_resid.h

@@ -4,7 +4,7 @@
 #ifdef __cplusplus
 extern "C" {
 #endif
-void   *sid_init();
+void   *sid_init(void);
 void    sid_close(void *p);
 void    sid_reset(void *p);
 uint8_t sid_read(uint16_t addr, void *p);