moved the Map<String,String>.toProperties() helper function into the standard library and added a test case

libraries/stdlib/test/MapTest.kt

@@ -187,4 +187,12 @@ class MapTest {
     }
     */
 
+    test fun toProperties() {
+        val map = hashMap("a" to "A", "b" to "B")
+        val prop = map.toProperties()
+        assertEquals(2, prop.size)
+        assertEquals("A", prop.getProperty("a", "fail"))
+        assertEquals("B", prop.getProperty("b", "fail"))
+    }
+
 }