xfce4-icon-theme: add dependency on intltool-native

* fails without it:
  | NOTE: Executing intltoolize --copy --force --automake
  | xfce4-icon-theme/4.4.3-r0/temp/run.do_configure.2826:
    intltoolize: not found
  | ERROR: Function failed: do_configure (log file is located at
    xfce4-icon-theme/4.4.3-r0/temp/log.do_configure.2826)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>