wasted work in "StaticTypeCheckingVisitor.inferReturnTypeGenerics"

The problem appears in version 2.0.5 and in revision 4cf5263.. I
attached a one-line patch that fixes it. I will also post (in the
"Comments" section) the URL for the github pull request.

There is no Groovy test that touches this code location (the entire
"else" branch that contains this code is not touched), but I think the
patch is correct.

In method "StaticTypeCheckingVisitor.inferReturnTypeGenerics", the
loop over "interfaces" should break immediately after "actualType" is
set. All the iterations after "actualType" is set do not perform any
useful work.