We currently show the inheritance diagram at the top of each class page,
but not at the top of interface pages, the reason being that interfaces
have multiple inheritance.

We should do a survey to see how many interfaces actually use multiple
inheritance; if it is small, then perhaps we should do as we do
in the "Tree" page (package-tree.html):

com.package1.Interface1
   com.package1.SubInterface (also extends java.io.Serializable)

Perhaps we could relgate mixin-type interfaces to the parenthetical
position, such as Serializable, Comparable, etc.