Headset Maker Plantronics Surfs on Games Wave  MILAN (Reuters) - Blockbuster video games and cheap  Internet phone calls are boosting demand for Plantronics'  &lt;A HREF="http://www.reuters.co.uk/financeQuoteLookup.jhtml?ticker=PLT.N qtype=sym infotype=info qcat=news"&gt;PLT.N&lt;/A&gt; headsets, the chief executive of the world's leading  maker of phone headsets said on Wednesday.