Add smooth scrolling for webkit browsers (#19097).

Patch by Felix Gliesche.

git-svn-id: http://svn.redmine.org/redmine/trunk@14818 e93f8b46-1217-0410-a6f0-8f06a7374b81

public/stylesheets/responsive.css

@@ -64,6 +64,8 @@
         overflow-x: hidden; /* hide horizontal overflow */
 
         min-width: 0; /* reset the min-width of 900px */
+
+        -webkit-overflow-scrolling: touch;
     }