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/varargsAndOut2.kt

@@ -0,0 +1,9 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+fun bar(vararg a: String) {}
+
+fun test2(a: Array<String>, b: Array<out String>) {
+    bar(*a)
+    bar(*b)
+    bar("", *a, *b, "")
+}