postproc.c: [nfc] use a C99 bool for 'Flip' instead of a boolean

diff --git a/lib/common/postproc.c b/lib/common/postproc.c
index 2cba534295de6e4dcbe151d4231aac3e6f28297f..1daa7a8aedb3fda0c44c0d21314857f69f6c997c 100644 (file)
--- a/lib/common/postproc.c
+++ b/lib/common/postproc.c
@@ -11,9 +11,10 @@
 
 #include <common/render.h>
 #include <label/xlabels.h>
+#include <stdbool.h>
 
 static int Rankdir;
-static boolean Flip;
+static bool Flip;
 static pointf Offset;
 
 static void place_flip_graph_label(graph_t * g);