[xml] Adding a build/configure *option* to use ICU converters

["Jungshik Shin" <jshin1987 gmail com>]

Hi,

Some non-Gnome projects on non-Linux platforms use libxml2, but they
also relyon ICU for character encoding conversion in the rest of the
project. They end
up having two sets of character encoding converters,  iconv and ICU
converters, which can increase the download size significantly.

For those projects, it'd be very nice to have a configuration option
in libxml2 that allow them
to use ICU converters rather than libiconv.

I made a preliminary patch and uploaded it to bugzilla (
http://bugzilla.gnome.org/show_bug.cgi?id=480323 ).
It works well on Windows, but I haven't yet managed to change
configure.in so that it has an 'with-icu' option.

I wonder what others think about this.  It'd be also nice if somebody
could help me with patching configure.in and related files to add
'-with-icu' option.

Thank you in advance,

Jungshik