If the new value and old value are the same, do not update the option in update_option().

git-svn-id: https://develop.svn.wordpress.org/trunk@1446 602fd350-edb4-49c9-b593-d223f7449a82

wp-includes/functions.php

@@ -320,6 +320,12 @@ function update_option($option_name, $newvalue) {
 	global $wpdb, $cache_settings;
 	$newvalue = $newvalue;
 	$newvalue = trim($newvalue); // I can't think of any situation we wouldn't want to trim
+
+    // If the new and old values are the same, no need to update.
+    if ($newvalue == get_settings($option_name)) {
+        return true;
+    }
+
 	$newvalue = $wpdb->escape($newvalue);
 	$wpdb->query("UPDATE $wpdb->options SET option_value = '$newvalue' WHERE option_name = '$option_name'");
 	$cache_settings = get_alloptions(); // Re cache settings