stand-alone info: Strange behavior when returning to the dir node

* for stand-alone info 7.2:

1. execute the command: info texinfo
2. press "u", we return to the dir node, the cursor is on the first line:

File: dir,      Node: Top       This is the top of the INFO tree

* for stand-alone info 7.3dev (50dc4a8d)

1. execute the command: info texinfo
2. press "u", we return to the dir node, the cursor is on the line:

* dir 1: (/usr/local/share/info/dir)Top.

* for emacs info mode:

1. evaluate: (info "texinfo")
2. press "u", we return to the dir node, the cursor is on the line:

* Texinfo: (texinfo).           The GNU documentation format.



Generally, when using M-x up-node, the cursor should jump to the
corresponding item in the menu of the up node.

Therefore, for these three behaviors, I think Emacs' Info mode is the most
reasonable. The behavior in Info 7.2 is also acceptable, but the current
behavior in Info 7.3dev seems very strange to me.