Editor: Disable `wp_keep_scroll_position` in IE11 since buggy; fix `matches` polyfill conflict with ME.js by doing runtime feature detection in context window.

Props westonruter, SergeyBiryukov, Clorith for testing.
See #41962, #42029.
Fixes #42553 for trunk.

Built from https://develop.svn.wordpress.org/trunk@42191


git-svn-id: http://core.svn.wordpress.org/trunk@42021 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/edit-form-advanced.php

@@ -639,7 +639,7 @@ if ( post_type_supports($post_type, 'editor') ) {
 		'resize' => false,
 		'wp_autoresize_on' => $_wp_editor_expand,
 		'add_unload_trigger' => false,
-		'wp_keep_scroll_position' => true,
+		'wp_keep_scroll_position' => ! $is_IE,
 	),
 ) ); ?>
 <table id="post-status-info"><tbody><tr>

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.0-alpha-42189';
+$wp_version = '5.0-alpha-42191';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.
@@ -18,7 +18,7 @@ $wp_db_version = 38590;
  *
  * @global string $tinymce_version
  */
-$tinymce_version = '4607-20170918';
+$tinymce_version = '4607-20171115';
 
 /**
  * Holds the required PHP version