Depending on which version of libiconv you're using, php_iconv_string()
doesn't always null out *out as part of its initialization. This
patch makes that behavior invariant.
Submitted upstream as https://github.com/php/php-src/pull/3037 where
it's approved and waiting a merge.
Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>
