[devhelp] Book: add FIXME comment

[Sébastien Wilmet <swilmet src gnome org>]

commit b6263e7f8559eb5e50b781805e7e700f87b2232d
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Sun Dec 10 10:52:46 2017 +0100

    Book: add FIXME comment
    
    No, I'm sure it's not the only way. It's just software, everything is
    possible.

 src/dh-book.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/src/dh-book.c b/src/dh-book.c
index 4f9844a..ea08eff 100644
--- a/src/dh-book.c
+++ b/src/dh-book.c
@@ -317,8 +317,9 @@ dh_book_new (GFile *index_file)
         }
 
         /* Rewrite language, if any, including the prefix we want to use when
-         * seeing it. It is pretty ugly to do it here, but it's the only way of
-         * making sure we standarize how the language group is shown.
+         * seeing it, to standarize how the language group is shown.
+         * FIXME: do this in DhLanguage instead (this may require to implement
+         * DhLanguage differently).
          */
         dh_util_ascii_strtitle (language);
         priv->language = (language != NULL ?