specify icon size in manage_main listings so the table doesn't jump around while the icons load

doc/CHANGES.txt

@@ -237,6 +237,9 @@ Zope Changes
 
     Bugs Fixed
 
+      - Specified height/width of icons in ZMI listings so the table doesn't
+        jump around while loading.
+
       - Acquisition wrappers now correctly proxy __iter__.
 
       - Launchpad #174705:  ensure that the error info object exposed to a

lib/python/OFS/dtml/main.dtml

@@ -133,7 +133,7 @@ function toggleSelect() {
   <a href="&dtml.url_quote-sequence-key;/manage_workspace">
   <dtml-in om_icons mapping>
   <img src="&dtml-BASEPATH1;/&dtml.url_quote-path;" alt="&dtml.missing-alt;" 
-   title="&dtml.missing-title;" border="0" /></dtml-in></a>
+   title="&dtml.missing-title;" border="0" width="16" height="16"/></dtml-in></a>
   <dtml-else>
 
   <dtml-if icon>