Add appdata.xml, provided by Matej Cepl.

AppData is an emerging standard (hopefully not distro-specific) for the
description of applications in various app stores.

http://people.freedesktop.org/~hughsient/appdata/ is the home page of
the standard.

http://blogs.gnome.org/hughsie/2013/09/27/frikin-awesome-apps-without-appdata/
is the call for providing new appdata.xml files.

RELEASE-NOTES

@@ -49,9 +49,6 @@ Interface changes
 - The Advanced Find and Replace feature now supports cancel of a
   long search operation by hitting the ESC key.
 
-- Linux desktop file specification and scalable icon has been
-  included in the tarball.
-
 - The format pdf aka "PDF (ps2pdf)" was split in two formats: pdf aka
   "PDF (ps2pdf)" and pdf6 aka "PDF (graphics)". pdf6 is used for PDF
   files included as graphics. Custom external templates and converters
@@ -188,6 +185,15 @@ The following LyX documents have been moved:
   from templates to examples (see #8643).
 
 
+The following metadata files have been added to the tarball:
+
+- Linux desktop file specification and scalable icon has been
+  included in the tarball.
+
+- AppData file (appdata.xml). It will not be installed by default and
+  distribution maintainers need to handle this file themselves.
+
+
 Changes with respect to external programs and libraries:
 --------------------------------------------------------
 

lib/Makefile.am

@@ -13,6 +13,7 @@ dist_pkgdata_DATA = CREDITS autocorrect chkconfig.ltx external_templates \
 dist_pkgdata_DATA += configure.py 
 
 dist_noinst_DATA = \
+	appdata.xml \
 	fonts/stmary10.sfd \
 	fonts/test/stmary10.lyx \
 	images/README \

lib/appdata.xml

@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="utf-8"?>
+<application>
+  <id type="desktop">lyx.desktop</id>
+  <licence>GPL-2</licence>
+  <name>LyX</name>
+  <summary>The Document Processor</summary>
+  <description>
+    <p>LyX is a document processor that encourages an approach to
+    writing based on the structure of your documents (WYSIWYM) and
+    not simply their appearance (WYSIWYG).</p>
+    <p>LyX combines the power and flexibility of TeX/LaTeX with the
+    ease of use of a graphical interface. This results in
+    world-class support for creation of mathematical content (via a
+    fully integrated equation editor) and structured documents like
+    academic articles, theses, and books. In addition, staples of
+    scientific authoring such as reference list and index creation
+    come standard. But you can also use LyX to create a letter or a
+    novel or a theatre play or film script. A broad array of ready,
+    well-designed document layouts are built in.</p>
+    <p>LyX is for people who want their writing to look great,
+    right out of the box. No more endless tinkering with formatting
+    details, “finger painting” font attributes or futzing around
+    with page boundaries. You just write. On screen, LyX looks like
+    any word processor; its printed output — or richly
+    cross-referenced PDF, just as readily produced — looks like
+    nothing else.</p>
+  </description>
+  <screenshots>
+    <screenshot type="default" width="1000" height="814">http://www.lyx.org/images/about/main_window.png</screenshot>
+    <screenshot width="623" height="431">http://www.lyx.org/images/about/preview_dvi.png</screenshot>
+    <screenshot width="962" height="720">http://www.lyx.org/images/about/edit_menu.png</screenshot>
+  </screenshots>
+  <url type="homepage">http://www.lyx.org</url>
+  <updatecontact>lyx-devel@lists.lyx.org</updatecontact>
+</application>