Revert commit because two commits fixing separate bugs were accidentally stuck together. Will recommit bugfixes separately.

Revert "KT-2193 Nullability information lost for functions inherited from traits".

This reverts commit d60818fd3e.

compiler/testData/codegen/traits/inheritedFun.jet

@@ -1,10 +0,0 @@
-//KT-2206
-trait A {
-    fun f():Int = 239
-}
-
-class B() : A
-
-fun box() : String {
-    return if (B().f() == 239) "OK" else "fail"
-}

compiler/testData/codegen/traits/inheritedVar.jet

@@ -1,14 +0,0 @@
-//KT-2206
-
-trait A {
-    var a:Int
-        get() = 239
-        set(value) {
-        }
-}
-
-class B() : A
-
-fun box() : String {
-    return if (B().a == 239) "OK" else "fail"
-}