Add two files on PLIST
+share/appdata/emacs.appdata.xml
+share/emacs/${PKGVERSION}/etc/emacs.appdata.xml
(Related commit log of upstream)
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  2014-08-28  Glenn Morris  <rgm@gnu.org>
  	* Makefile.in (appdatadir): New variable.
  	(install-etc, uninstall, clean): Handle etc/emacs.appdata.xml.
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