[emf] set bundle dependencies to emf >=2.9

[api-tool] added missing api_filters files

[xtext] lower bound for xtext dependencies set to 2.4.2

[xtend] lower bound for xtend dependencies set to 2.4.2
Merge "[emf] set bundle dependencies to emf >=2.9"
[generator] Added some explanation to the generateXtendStub flag
https://bugs.eclipse.org/bugs/show_bug.cgi?id=405321

Change-Id: I4a7ce2bc0008796ce11ddb39cb623bf961e84944
[organizeImports] Fix: ValueConverterException on organize imports

This fixes a regression due to the application of value converters
on organize imports

see https://bugs.eclipse.org/bugs/show_bug.cgi?id=406301

Change-Id: I6fa6c9021d187debbc80f7e383b29882fe327208
[xbase][typesystem] Fix: CME on map.values.sort

see https://bugs.eclipse.org/bugs/show_bug.cgi?id=406267

Change-Id: I6f36d0ba533772e6615eddc6c7e9fc031cf2dbc0
[benchmark] Compare visitors with polymorphic dispatching

see https://bugs.eclipse.org/bugs/show_bug.cgi?id=406337
[xtend][typesystem] Improved inference of constraint type arguments

Example:

interface Bound<T extends Number> {
    def void method(T t);
}
class Test {
    def static void test(Bound<?> b) {
    }
    def static void main(String[] args) {
        test [
        ]
    }
}

The method #test declares a parameter Bound<? extends Object> though
the type parameter T has to be at least Number when the instance
of an anonymous subtype of Bound is created in #main.

see https://bugs.eclipse.org/bugs/show_bug.cgi?id=405825

Change-Id: Ifed9fa502e30246ade22be5fcc28bef973c628e5
[xbase][typesystem] Improve resolution of type arguments in var arg context

Both pairs in the following expression are typed as expected, e.g.

newHashMap( 5 -> '', '' -> 5 )

Pair<Integer, String> and Pair<String, Integer> and
the produced map is a
HashMap<Comparable<?> & Serializable, Comparable<?> & Serializable>

which boils down to HashMap<Object, Object> on the Java side

see https://bugs.eclipse.org/bugs/show_bug.cgi?id=406051

Change-Id: Iffb0eb327c594234cc0c5ca1f1459396add165a4
[xtend][compiler] Proper generation of type parameters

Return value 'null' was not assigned to a type parameter
even though the type system properly identified it as such

see https://bugs.eclipse.org/bugs/show_bug.cgi?id=406356

Change-Id: Ia42e1d38bbb0f2e5896dcfcae6c825585d6daa6e