[balsa] Add balsa.appdata.xml to po/POTFILES.in

[Peter Bloomfield <peterb src gnome org>]

commit 4880b0da392c01b47b60f3aab4daaccdd7ac3d57
Author: Peter Bloomfield <PeterBloomfield bellsouth net>
Date:   Sat Aug 19 13:40:05 2017 -0400

    Add balsa.appdata.xml to po/POTFILES.in
    
    Piotr Drąg pointed out in
    https://bugzilla.gnome.org/show_bug.cgi?id=786515 that
    balsa.appdata.xml is not hooked up for translation.

 po/POTFILES.in |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/po/POTFILES.in b/po/POTFILES.in
index 355a696..8b6776d 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -1,6 +1,7 @@
 [encoding: UTF-8]
 # List of source files containing translatable strings.
 # Please keep this list in alphabetical order.
+balsa.appdata.xml
 balsa.desktop.in.in
 balsa-mailto-handler.desktop.in.in
 libbalsa/address-book.c