Give plugins the ability to do extra processing on a post before it is inserted/updated. See #5196.

git-svn-id: https://develop.svn.wordpress.org/trunk@8635 602fd350-edb4-49c9-b593-d223f7449a82

wp-admin/edit-form-advanced.php

@@ -147,6 +147,7 @@ if ( 0 != $post_ID ) {
 </div>
 
 <p class="submit">
+<?php do_action('post_submitbox_start'); ?>
 <input type="submit" name="save" id="save-post" value="<?php _e('Save'); ?>" tabindex="4" class="button button-highlighted" />
 <?php
 if ( !in_array( $post->post_status, array('publish', 'future') ) || 0 == $post_ID ) {