KT-127 Support extension functions in when expressions

compiler/testData/checkerWithErrorTypes/quick/regressions/kt127.jet

@@ -0,0 +1,15 @@
+// KT-127 Support extension functions in when expressions
+
+class Foo() {}
+
+fun Any.equals(other : Any?) : Boolean = true
+fun Any?.equals1(other : Any?) : Boolean = true
+
+fun main(args: Array<String>) {
+
+    val command : Foo? = null
+    when (command) {
+      .equals(null) => 1; // must be resolved
+      ?.equals(null) => 1 // same here
+    }
+}