Mail-Order Drugs Bite Into Rite Aid Sales  CHICAGO (Reuters) - Drugstore chain Rite Aid Corp. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=RAD.N target=/stocks/quickinfo/fullquote"&gt;RAD.N&lt;/A&gt;  on Tuesday warned that full-year profit and revenue would fall  short of expectations as it loses pharmacy sales to mail-order  rivals, sending its shares down 16 percent.