Accessibility: Fix the Customizer available menu items toggles focus for Safari and VoiceOver.

In rare circumstances, for example buttons with icons and no visible text,
`user-select: none;` may trigger a bug that happens only when using Safari and
VoiceOver and doesn't allow focusable elements to receive focus correctly.
Worth reminding `user-select: none;` is a non-standard property and should be
used with care especially now that `::selection` is almost universally supported.

Fixes #37589.

Built from https://develop.svn.wordpress.org/trunk@38642


git-svn-id: http://core.svn.wordpress.org/trunk@38585 1a063a9b-81f0-0310-95a4-ce76da25c4cd

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

@@ -482,6 +482,11 @@
 	background: #fff;
 	-webkit-transition: background-color 0.15s;
 	transition: background-color 0.15s;
+	/* Reset the value inherited from the base .accordion-section-title style. Ticket #37589. */
+	-webkit-user-select: auto;
+	-moz-user-select: auto;
+	-ms-user-select: auto;
+	user-select: auto;
 }
 
 #available-menu-items .open .accordion-section-title,

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

@@ -482,6 +482,11 @@
 	background: #fff;
 	-webkit-transition: background-color 0.15s;
 	transition: background-color 0.15s;
+	/* Reset the value inherited from the base .accordion-section-title style. Ticket #37589. */
+	-webkit-user-select: auto;
+	-moz-user-select: auto;
+	-ms-user-select: auto;
+	user-select: auto;
 }
 
 #available-menu-items .open .accordion-section-title,

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.7-alpha-38641';
+$wp_version = '4.7-alpha-38642';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.