function _fnCallbackReg( oSettings, sStore, fn, sName )
	{
		if ( fn )
		{
			oSettings[sStore].push( {
				"fn": fn,
				"sName": sName
			} );
		}
	}
Register a callback function. Easily allows a callback function to be added to
an array store of callback functions that can then all be called together.
 @param {object} oSettings dataTables settings object
 @param {string} sStore Name of the array storage for the callbacks in oSettings
 @param {function} fn Function to be called back
 @param {string} sName Identifying name for the callback (i.e. a label)
 @memberof DataTable#oApi