TinyMCE:

- Fix toolbar icons in IE9.
- Remove background gradients in IE < 10.
- Lint our plugins.
- Add draggable attribute to the caption wrapper and make the captioned images non-draggable in Chrome.
See #24067.
Built from https://develop.svn.wordpress.org/trunk@26880


git-svn-id: https://core.svn.wordpress.org/trunk@26763 1a063a9b-81f0-0310-95a4-ce76da25c4cd