Apple Enhances iBook, Cuts Prices Before Holidays  SAN FRANCISCO (Reuters) - Apple Computer Inc. &lt;A HREF="http://www.reuters.co.uk/financeQuoteLookup.jhtml?ticker=AAPL.O qtype=sym infotype=info qcat=news"&gt;AAPL.O&lt;/A&gt; on  Tuesday announced a faster version of its popular iBook  notebook personal computer and a less expensive model of its  PowerMac desktop line, as the computer maker gears up for the  holiday shopping season.