Adding support for theme='' parameter in {exp:forum} tag

mod.forum.php

        /**                
	        This core hack in mod.forum.php will enable you to load a different forum theme from different templates.
			Append in the constructor, just after $this->_load_base() like shown below.                    
        */



	    /** -------------------------------------
	    /**  Load Base Forum Variables
	    /** -------------------------------------*/
                
        $this->_load_base();

        /**
         * Did we specify a different theme to be used in the {exp:forums} tag?
         */
        if(isset($this->EE->TPML) && $this->EE->TMPL->fetch_param('theme'))
        {
            $this->theme =  $this->EE->TMPL->fetch_param('theme');
        }