Merge boxWithStdlib testData into box, delete BoxWithStdlib test

compiler/testData/codegen/box/regressions/kt1779.kt

@@ -0,0 +1,20 @@
+// WITH_RUNTIME
+
+import kotlin.collections.AbstractIterator
+
+class MyIterator : AbstractIterator<String>() {
+    var i = 0
+    public override fun computeNext() {
+        if(i < 5)
+          setNext((i++).toString())
+    }
+
+}
+
+fun box() : String {
+    var k = ""
+    for (x in MyIterator()) {
+        k+=x
+    }
+    return if(k=="01234") "OK" else k
+}