Using iconv in stand-alone info

[Eli Zaretskii]

I noticed that info-utils.c doesn't call 'iconv' one last time after
the conversion is finished.  This is required to output the last
character when the conversion is implemented by libiconv as a stateful
one.

See this discussion on Wget mailing list about one such problem:

  http://lists.gnu.org/archive/html/bug-wget/2015-12/msg00111.html
  http://lists.gnu.org/archive/html/bug-wget/2015-12/msg00113.html

So I suggest we fix this in Info by adding a call to 'iconv' when the
conversion returns with success.

Thanks.