Minor: moved test for check the iterating over String to common place.

#KT-3617 Fixed

libraries/stdlib/test/text/StringJVMTest.kt

@@ -6,13 +6,6 @@ import kotlin.test.*
 import org.junit.Test as test
 
 class StringJVMTest {
-    test fun stringIterator() {
-        var sum = 0
-        for(c in "239")
-            sum += (c.toInt() - '0'.toInt())
-        assertTrue(sum == 14)
-    }
-
     test fun stringBuilderIterator() {
         var sum = 0
         val sb = StringBuilder()

libraries/stdlib/test/text/StringTest.kt

@@ -127,4 +127,11 @@ class StringTest {
         assertEquals("xxx", s.replaceBefore("=", "new name", "xxx"))
         assertEquals("xxx", s.replaceBeforeLast("=", "/new/path", "xxx"))
     }
+
+    test fun stringIterator() {
+        var sum = 0
+        for(c in "239")
+            sum += (c.toInt() - '0'.toInt())
+        assertTrue(sum == 14)
+    }
 }