[PATCH] Allow ndisgen to work without libiconv port

[Dave Vasilevsky]

Currently, ndisgen refuses to process UTF-16 .inf files unless
libiconv is installed. Unfortunately, if you need ndis you probably
don't have a net connection, which makes it hard to get libiconv.

This patch works around the problem by integrating a very small UTF-16
to UTF-8 converter into ndiscvt. It auto-detects UTF-16 encoding, so
it should Just Work on any .inf file.

http://www.freebsd.org/cgi/query-pr.cgi?pr=179285

I'd appreciate testing against various .inf files, to ensure it's
working right. Code review would also be great, especially by anyone
with a commit bit :)

Cheers,
Dave