Fix build error due to bool keyword with gcc-15

* gcc-15 uses gnu23 for c.
  'bool' is a keyword.
TOPDIR/tmp/work/core2-64-oe-linux/paho-mqtt-c/1.3.14/git/src/MQTTPacket.h:31:22: error: 'bool' cannot be defined via 'typedef'
   31 | typedef unsigned int bool;
      |                      ^~~~
TOPDIR/tmp/work/core2-64-oe-linux/paho-mqtt-c/1.3.14/git/src/MQTTPacket.h:31:22: note: 'bool' is a keyword with '-std=c23' onwards
TOPDIR/tmp/work/core2-64-oe-linux/paho-mqtt-c/1.3.14/git/src/MQTTPacket.h:31:1: warning: useless type name in empty declaration
   31 | typedef unsigned int bool;
      | ^~~~~~~

Signed-off-by: mark.yang <mark.yang@lge.com>
Signed-off-by: markyang92 <pllpokko@alumni.kaist.ac.kr>

Author: markyang-lge

src/MQTTPacket.h

@@ -28,7 +28,9 @@
 #include "LinkedList.h"
 #include "Clients.h"
 
+#if defined __STDC__ && defined __STDC_VERSION__ && __STDC_VERSION__ <= 201710L
 typedef unsigned int bool;
+#endif
 typedef void* (*pf)(int, unsigned char, char*, size_t);
 
 #include "MQTTProperties.h"