Use stdbool.h for compatibility with C23.

--- rpcemu-0.9.5/src/hostfs.c	2024-10-23 20:46:07.000000000 +0100
+++ rpcemu-0.9.5/src/hostfs.c	2025-07-11 00:07:20.654497757 +0100
@@ -21,6 +21,7 @@
 #include <ctype.h>
 #include <errno.h>
 #include <stdarg.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -51,11 +52,6 @@
 # define mkdir(name, mode) _mkdir(name)
 #endif
 
-typedef int bool;
-
-#define true  ((bool) 1)
-#define false ((bool) 0)
-
 /** Registration states of HostFS module with backend code */
 typedef enum {
   HOSTFS_STATE_UNREGISTERED,	/**< Module not yet registered */