add support for override analysis

[monperrus]

We have a transformation that requires a method that gives the overridden method.

CtMethod {
  // returns the overridden method, null if none 
  CtMethod getOverridenMethod()

}

[monperrus]

to get the first declaration of the method it would be something like:

m = meth.getOverridenMethod();
while (m!=null)  {
  m = m.getOverridenMethod();
}

[monperrus]

should it be CtExecutableReferene getOverridenMethod()?

[monperrus]

the implementation may reuse CtExecutableReference.isOverriding()

[GerardPaligot]

We should talk where we put this method. I don't think we should put it in the AST but in a query space where we can put utility methods like this one.

[GerardPaligot]

2 filters for this issue:

• OverridenMethodFilter where 0 is the top overriden method.
• OverridingMethodFilter to get all method below the current method overriden or declared excluding itself.