Mark appdata for translation

data/Makefile.am

@@ -9,7 +9,9 @@ desktop_DATA = $(desktop_in_files:.desktop.in=.desktop)
 @INTLTOOL_DESKTOP_RULE@
 
 appdatadir = $(datadir)/appdata
-appdata_DATA = gnome-sudoku.appdata.xml
+appdata_in_files = gnome-sudoku.appdata.xml.in
+appdata_DATA = $(appdata_in_files:.xml.in=.xml)
+@INTLTOOL_XML_RULE@
 
 pixmapdir = $(datadir)/gnome-sudoku/images/
 pixmap_DATA = footprints.png
@@ -32,13 +34,14 @@ man_MANS = gnome-sudoku.6
 EXTRA_DIST = \
 	$(pixmap_DATA)	\
 	$(desktop_in_files) \
-	$(appdata_DATA)	\
+	$(appdata_in_files)	\
 	$(puzzle_DATA)	\
 	$(ui_DATA)	\
 	$(gsettings_SCHEMAS) \
 	$(man_MANS)
 
 CLEANFILES = \
+	$(appdata_DATA) \
 	$(desktop_DATA)
 
 check-local: $(appdata_DATA) $(desktop_DATA)

data/gnome-sudoku.appdata.xml → data/gnome-sudoku.appdata.xml.in

@@ -2,28 +2,28 @@
 <application>
 <id type="desktop">gnome-sudoku.desktop</id>
 <licence>CC0</licence>
-<name>GNOME Sudoku</name>
+<_name>GNOME Sudoku</_name>
 <description>
-<p>
+<_p>
 GNOME Sudoku has a simple unobstrusive interface
 while still providing features that make playing difficult Sudoku more fun.
 All games are automatically saved when you quit so you don't have to worry about saving games.
 You can always come back to any game you've played.
-</p>
-<p>
+</_p>
+<_p>
 If you like to play on paper, you can print games out.
 You can choose how many games you want to print per page and what difficulty of
 games you want to print: as a result, GNOME Sudoku can act a renewable Sudoku Book for you.
-</p>
-<p>
+</_p>
+<_p>
 Each game is assigned a "difficulty" score - its algorithm generally does a good
 job matching the difficulty rankings typically given by newspapers and websites.
 You can also see detailed difficulty information about how the computer solved
 the puzzle.
-</p>
+</_p>
 </description>
 <screenshots>
-<screenshot type="default" width="800" height="447">https://people.gnome.org/~mcatanzaro/gnome-sudoku.png</screenshot>
+<_screenshot type="default" width="800" height="447">https://people.gnome.org/~mcatanzaro/gnome-sudoku.png</_screenshot>
 </screenshots>
 <url type="homepage">https://wiki.gnome.org/GnomeSudoku</url>
 <updatecontact>games-list_at_gnome.org</updatecontact>

po/POTFILES.in

 # List of source files containing translatable strings.
 # Please keep this file in alphabetical order.
 [encoding: UTF-8]
+data/gnome-sudoku.appdata.xml.in
 data/gnome-sudoku.desktop.in
 data/org.gnome.gnome-sudoku.gschema.xml
 [type: gettext/glade]data/print_games.ui