dictobject.c: explain why stringlib is used
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 8a13fb4..91a4e7d 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -111,7 +111,7 @@
 
 #include "Python.h"
 #include "dict-common.h"
-#include "stringlib/eq.h"
+#include "stringlib/eq.h"    /* to get unicode_eq() */
 
 /*[clinic input]
 class dict "PyDictObject *" "&PyDict_Type"