KT-2632 Check multi-declaraions in for-loops

#KT-2632 Fixed

compiler/testData/diagnostics/tests/declarationChecks/multiDeclarations/SingleDeclForLoop.kt

@@ -0,0 +1,13 @@
+class A {
+    fun component1() = 1
+}
+
+class C {
+    fun iterator(): Iterator<A> = null!!
+}
+
+fun test() {
+    for ((x) in C()) {
+
+    }
+}