KT-2498 Bridge method is not generated for method when generic parameters are substituted in superclass

#KT-2498 Fixed

generateBridgeIfNeeded() now works as follows: for a given method, find
which declared methods does this method override via breadth-first search.
For each such declared method, generate a bridge if and only if its
signature is different. Keep different methods' signatures in a set to
avoid duplicated bridge signatures.

compiler/testData/codegen/bridges/substitutionInSuperClassObject.kt

@@ -0,0 +1,25 @@
+open class A<T> {
+    open fun foo(t: T) = "A"
+}
+
+open class B : A<String>()
+
+object Z : B() {
+    override fun foo(t: String) = "Z"
+}
+
+
+fun box(): String {
+    val o = object : B() {
+        override fun foo(t: String) = "o"
+    }
+    return when {
+        Z.foo("")               != "Z" -> "Fail #1"
+        o.foo("")               != "o" -> "Fail #2"
+        (Z : B).foo("")         != "Z" -> "Fail #3"
+        (o : B).foo("")         != "o" -> "Fail #4"
+        (Z : A<String>).foo("") != "Z" -> "Fail #5"
+        (o : A<String>).foo("") != "o" -> "Fail #6"
+        else -> "OK"
+    }
+}