[xml] iconv and zlib1 always needed on Windows?

[Jay Patrick Howard <jhoward feeding frenzy com>]

Am working on a project that uses libxml for very simple parsing and
wondered if it would be possible to not distribute iconv.dll and zlib1.dll
if my project doesn't use that functionality.  What conditions or calls
result in these being loaded?  So far our stuff seems to work correctly
when only libxml2.dll is present.

Thanks.