Check for old "LyX 2.3" user directory when configuring.

This is due to the bad packaging in the early 2.3.x installers. We
normally do not use version suffixes on Windows, but did.

lib/configure.py

@@ -181,6 +181,22 @@ def checkUpgrade():
                 return
 
 
+def checkUpgradeWin():
+    ''' Check for upgrade from previous version '''
+    cwd = os.getcwd()
+    basename = os.path.basename(cwd)
+    if basename != "LyX":
+        return
+    lyxrc = os.path.join(cwd, outfile)
+    if os.path.isfile(lyxrc):
+        return
+    olddir = os.path.join(os.path.dirname(cwd), "LyX2.3")
+    if not os.path.isdir(oldir):
+        return
+    logger.info('Copying ' + olddir + ' into ' + cwd)
+    copy_tree(olddir, cwd, True)
+
+
 def createDirectories():
     ''' Create the build directories if necessary '''
     for dir in ['bind', 'clipart', 'doc', 'examples', 'images', 'kbd',
@@ -1840,6 +1856,8 @@ Options:
     setEnviron()
     if sys.platform == 'darwin' and len(version_suffix) > 0:
         checkUpgrade()
+    if os.name == 'nt':
+        checkUpgradeWin()
     createDirectories()
     dtl_tools = checkDTLtools()
     ## Write the first part of outfile