Fix wp_mkdir_p() when running under safe_mode on certain PHP versions. Props Denis-de-Bernardy. Fixes #8830

git-svn-id: https://develop.svn.wordpress.org/trunk@12740 602fd350-edb4-49c9-b593-d223f7449a82

wp-includes/functions.php

@@ -1933,6 +1933,12 @@ function wp_get_original_referer() {
 function wp_mkdir_p( $target ) {
 	// from php.net/mkdir user contributed notes
 	$target = str_replace( '//', '/', $target );
+
+	// safe mode fails with trailing slash under certain PHP versions.
+	$target = untrailingslashit($target);
+	if ( empty($target) )
+		$target = '/';
+
 	if ( file_exists( $target ) )
 		return @is_dir( $target );