Show stack trace for fatal errors if xdebug is loaded.

src/Template/Error/fatal_error.ctp

@@ -30,3 +30,6 @@
 	<strong>Notice: </strong>
 	<?= sprintf('If you want to customize this error message, create %s', APP_DIR . DS . 'Template' . DS . 'Error' . DS . 'fatal_error.ctp'); ?>
 </p>
+<?php if (extension_loaded('xdebug')): ?>
+	<p><?php xdebug_print_function_stack(); ?></p>
+<?php endif; ?>