allow __player_audioplayer__ to build even when PortAudio is not present * __player_audioplayer__.cc: added conditional compilation constructs to prevent parts requiring PortAudio from being built if it is not present

%!function r = f (x)
%!  if (ischar (x))
%!    r = x;
%!  else
%!    error ("expecting character string");
%!  endif
%!endfunction

%!assert (eval ("f 10;"), "10");