Make all required includes explicit

Information as seen by IWYU 0.12 + clang 9 on Linux

1 files changed, 2 insertions, 0 deletions

diff --git a/ListItem.h b/ListItem.h
index 387e8e21..5bbcda14 100644
--- a/ListItem.h
+++ b/ListItem.h
@@ -7,6 +7,8 @@ Released under the GNU GPLv2, see the COPYING file
 in the source distribution for its full text.
 */
 
+#include <stdbool.h>
+
 #include "Object.h"
 
 typedef struct ListItem_ {