Build/Test: Bump Autoprefixer to 6.5.0

Also includes a new prefixed value.

Changes:
6.5 “Einigkeit und Recht und Freiheit”
- Add defaults keyword to browsers requirements.
- Fix CSS Grid Layout support.
- Fix align-self cleaning.

6.4.1
- Fix node cloning after some PostCSS plugins.

6.4 “Hic et ubique terrarum”
- Add :any-link selector support.
- Add text-decoration-skip support.
- Add transition: duration property support.
- Fix -webkit- prefix for backface-visibility.
- Fix rad unit support in gradients (by 刘祺).
- Fix transition support in Opera 12.
- Removed Safari TP Grid prefixes support.

6.3.7
- Fix rare Cannot read property 'constructor' of null issue.

6.3.6
- Add Safari TP prefix support for Grid Layout.

6.3.5
- Fix duplicate prefixes for -ms-interpolation-mode.

6.3.4
- Show users coverage for selected browsers in info().

28.0
- Happy Birthday @nacin

See #38199




git-svn-id: https://develop.svn.wordpress.org/trunk@38688 602fd350-edb4-49c9-b593-d223f7449a82

package.json

@@ -9,7 +9,7 @@
   "author": "The WordPress Contributors",
   "license": "GPL-2.0+",
   "devDependencies": {
-    "autoprefixer": "~6.3.3",
+    "autoprefixer": "^6.5.0",
     "grunt": "~0.4.5",
     "grunt-browserify": "~5.0.0",
     "grunt-contrib-clean": "~1.0.0",

src/wp-admin/css/customize-nav-menus.css

@@ -568,6 +568,7 @@
 }
 
 #available-menu-items .accordion-section-content .new-content-item {
+	width: -webkit-calc(100% - 30px);
 	width: calc(100% - 30px);
 	padding: 8px 15px;
 	position: absolute;