Add missing header include.

git-svn-id: https://geany.svn.sourceforge.net/svnroot/geany/trunk@3901 ea778897-0a13-0410-b9d1-a72fbfd435f5

src/toolbar.c

@@ -39,6 +39,7 @@
 #include "geanymenubuttonaction.h"
 #include "geanyentryaction.h"
 
+#include <string.h>
 #include <glib/gstdio.h>