add note that only all lowercase typedefed classes work

for custom components with add(type).


git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@275475 13f79535-47bb-0310-9956-ffa450edef68

docs/manual/CoreTypes/custom-programming.html

@@ -39,6 +39,8 @@
     <p>
       After the class has been written, it is added to the ant system
       by using <code>&lt;typedef&gt;</code>.
+      One thing to be aware of is that currently this will only work
+      if the definition name is all lower case.
     </p>
     <h3><a name="customconditions">Custom Conditions</a></h3>
     <p>