[patch binutils]: Fix build for cygwin and mingw of binutils tools

[Dave Korn]

Dave Korn wrote:

>   In this package, it's called libiconv_open() for some reason.  Hmm, this is
> bizarre; /usr/include/iconv.h and /usr/lib/libiconv{,.dll}.a disagree.  Ah, my
> libiconv installation must have gotten broken somehow.  I'll have to reinstall it.

  Fixing the broken header file did it; I can now reproduce the error and
verified that the patch fixes it.  Plus it is clearly correct from inspecting
the source, as all the calls to the functions are visibly wrapped in #ifdefs
that will exclude windows, so the functions themselves should also be.

    cheers,
      DaveK