Made vararg parameters have Array<out T> type

instead of simply Array<T>
  #KT-1638 Fixed
  #KT-2163 Fixed
  #KT-3213 Fixed
  #KT-4172 Fixed
  #KT-5534 Fixed

compiler/testData/diagnostics/tests/varargs/varargsAndPair.kt

@@ -0,0 +1,8 @@
+fun foo<T: Any>(vararg <!UNUSED_PARAMETER!>ts<!>: T): T? = null
+
+class Pair<A>(a: A)
+
+fun test() {
+    val v = foo(Pair(1))
+    <!TYPE_MISMATCH!>v<!>: Int // check that it is not error type
+}