Changes to Smarty_Compiler.class.php

Hi,

I've run into a problem with the current implementation of postfilters,
please refer to:
http://www.phpinsider.com/smarty-forum/viewtopic.php?p=28405

Basically, postfilters do not work exactly as it is documented so it becomes
practically impossible for plugins to modify the $smarty->plugins_dir. I
made some changes to Smarty_Compiler.class.php and attached the diff file so
that, hopfully, someone can fix the problem and have it work as expected per
documentation in the next release.

Changes to lines 371+:
 - Postfilter functions are applied after $template_header is prepended to
$compiled_content
 - Removal of unnecessary close/open tags happen immediately before return.

- David