Customize: Remove IE8 access to customizer to discontinue support.

Uses feature detection for `Array.prototype.indexOf` since it is not implemented in IE8.

Props ryankienstra.
See #38021.

Built from https://develop.svn.wordpress.org/trunk@38627


git-svn-id: http://core.svn.wordpress.org/trunk@38570 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/theme.php

@@ -2169,7 +2169,7 @@ function wp_customize_support_script() {
 <?php		endif; ?>
 
 			b[c] = b[c].replace( rcs, ' ' );
-			b[c] += ( window.postMessage && request ? ' ' : ' no-' ) + cs;
+			b[c] += ( window.postMessage && request && Array.prototype.indexOf ? ' ' : ' no-' ) + cs;
 		}());
 	</script>
 	<?php

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.7-alpha-38626';
+$wp_version = '4.7-alpha-38627';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.