Tinkering with the period size and number of periods. My informal testing

suggests this is more or less optimal.  Added new option to allow the
number of periods to be adjusted without needing to recompile.  Also fixed
an incorrect sound writing loop as per Jack's suggestion.


git-svn-id: http://svn.xiph.org/trunk/ao@1981 0101bb08-14d6-0310-b084-bc0e0c8e3800