7082231: Put a @since 1.7 on System.lineSeparator

Reviewed-by: mduigou

src/share/classes/java/lang/System.java

@@ -632,6 +632,7 @@ public final class System {
      *
      * <p>On UNIX systems, it returns {@code "\n"}; on Microsoft
      * Windows systems it returns {@code "\r\n"}.
+     * @since 1.7
      */
     public static String lineSeparator() {
         return lineSeparator;