Fixing GdbStub Code to make it compiled with Clang (#2292)

- Fix the switch scoping preventing declaration
- Adding stdint.h as inclusion to make uint*_t works

src/include/86box/gdbstub.h

@@ -16,6 +16,7 @@
  */
 #ifndef EMU_GDBSTUB_H
 #define EMU_GDBSTUB_H
+#include <stdint.h>
 #include <86box/mem.h>
 
 #define GDBSTUB_MEM_READ   0