Extend PanelOtherSync action in Panelize mode to show selected filename in other panel

[iwfmp]

From ​https://github.com/MidnightCommander/mc/issues/16:

Say I recursively list a folder called /somefolder. There is a file called /somefolder/in/another/sub/folder/file.txt that is listed using panelize. In total commander, double commander and whatever commander I can use a command called "view in other pane", which then cd's into /somefolder/in/another/sub/folder in the other pane to list file.txt and any other file that's in there. Or, in other words, showing the source file path in the other pane.

I think this can be "easily" implemented by extending panel_sync_other.