type of iconv return value -1?

[Simon Josefsson]

Shouldn't it be (iconv_t)-1 in charset.texi:

...
@code{(size_t) -1} and @code{errno} is set appropriately.  In such cases
...
      nconv = iconv (cd, &inptr, &insize, &wrptr, &avail);
      if (nconv == (size_t) -1)
...