Added the support of superstrings in the i18n annotation.
The first commit introduces a string format to use when replacing superstrings.
The second and third commits are updates to the i18n annotation and the test that goes along with it.
Pull-Request: #1319
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>
Reviewed-by: Jean Privat <jean@pryen.org>