introduce the defcustom php-template-compatibility

avoid all the stuff to deal with html when you know that you only use
php-mode only for plain php scripts
(moreover I sometime had a bug with the '>' character .. see the screenshot attached)
![emacs-php-mode](https://f.cloud.github.com/assets/959622/430809/9ad02524-ae77-11e2-85a3-1dcbe7f89bec.png)