Autoloader: fix missing return value

An autoloader should always return a boolean value to indicate whether or not it has loaded a file. This allows for chaining autoloaders.

In most cases, the `return` statement in the autoloader already returned a boolean, this was the only exception.

Author: jrfnl

autoload.php

@@ -73,7 +73,7 @@ public static function load($class)
                 // Make sure we don't try to load any of Composer's classes
                 // while the autoloader is being setup.
                 if (strpos($class, 'Composer\\') === 0) {
-                    return;
+                    return false;
                 }
 
                 if (strpos(__DIR__, 'phar://') !== 0