compile fix for x48-0.6.4 with gcc 15.2

x48-gcc15.patch

diff -ur src/src/debugger.c src-update/src/debugger.c
--- src/src/debugger.c	2011-11-14 19:03:40.000000000 -0800
+++ src-update/src/debugger.c	2025-09-04 18:19:21.821404084 -0700
@@ -1585,7 +1585,7 @@
   saturn.mem_cntl[1].config[0] = ram_base;
   saturn.mem_cntl[1].config[1] = ram_mask;
 
-  return;
+  return 0;
 }
 
 static void
diff -ur src/src/serial.c src-update/src/serial.c
--- src/src/serial.c	2011-11-14 19:03:40.000000000 -0800
+++ src-update/src/serial.c	2025-09-04 18:24:42.099491607 -0700
@@ -64,6 +64,7 @@
 #include "global.h"
 
 #include <stdio.h>
+#define __USE_XOPEN_EXTENDED
 #include <stdlib.h>
 #include <string.h>
 #include <fcntl.h>