Description
   This is the only dependency that accepts an ereg()able pattern.  The pattern 
   will be matched against the php_uname() output parsed by OS_Guess
   As with all dependency validation, true is returned on success, PEAR_Error on failure
   for required dependencies (and the arch dependency is required).  If the
   soft, force or ignore-errors
   options are specified, an array containing the error message will be returned instead.