[LyX/master] More informative name for backups of files from older versions.

[Richard Heck]

commit 82c3a44337875d29741c87c9fd380a7bddcf258a
Author: Richard Heck <rgh...@lyx.org>
Date:   Sun Mar 27 19:40:02 2016 -0400

    More informative name for backups of files from older versions.

diff --git a/src/Buffer.cpp b/src/Buffer.cpp
index 37dcbca..102b4ef 100644
--- a/src/Buffer.cpp
+++ b/src/Buffer.cpp
@@ -1321,7 +1321,7 @@ FileName Buffer::getBackupName() const {
                fn.onlyPath().absFileName() :
                lyxrc.backupdir_path;
        string const fform = convert<string>(d->file_format);
-       string const backname = fname + "-" + fform;
+       string const backname = fname + "-lyxformat-" + fform;
        FileName backup(addName(fpath, addExtension(backname, fext)));
 
        // limit recursion, just in case