When going back to the previous buffer from shell buffer and that
buffer no longer exists, something goes wrong. That is, we visit
no-longer-existing buffer by creating it. This is not what we want it
Renamed collect-same-mode-buffer to shell-pop-collect-same-mode-buffer.
Add some documentation and corerct indentation.
Some correction made on function collect-same-mode-buffer.
Made some progress.
Removed some garbage left.
Updated to the latest.