Delete skins/common/{ajax.js, wikibits.js, images/{magnify-clip-rtl.png, redirectltr.png, redirectrtl.png}}

* ajax.js, wikibits.js:
  Was kept for third parties. (user scripts etc.)
* redirectltr.png, redirectrtl.png:
  Was kept for cached stylesheets, after I8fa565833545e41d02 removed
  usage in MediaWiki core.
* magnify-clip-rtl.png:
  Was kept for third parties. (user scripts etc.)

Bug: 69277
Change-Id: I54b170b557414e2f3cda4c85053cd0f2cbefc10d
Merge "Delete skins/common/{ajax.js, wikibits.js, images/{magnify-clip-rtl.png, redirectltr.png, redirectrtl.png}}"