Fix windows header inclusion (#1324)

WIN32_LEAN_AND_MEAN strips many header
inclusions from windows.h to speed up build
times. It appears to strip windef.h which
is needed for FALSE/TRUE.

Author: kstribrnAmzn

source/portable/NetworkInterface/libslirp/MBuffNetworkInterface.c

@@ -29,6 +29,8 @@
 
 #if defined( _WIN32 )
     #include <windows.h>
+    /* Required when compiling with WIN32_LEAN_AND_MEAN as it strips this header which defines TRUE/FALSE */
+    #include <windef.h>
 #endif
 
 /* FreeRTOS includes. */