Tramp patch for emacs-24 branch

[Michael Albinus]

Hi,

Last days, I have worked on a fix for a nasty Tramp problem: it loads
itself recursively, when default-directory is already a remote file
name. One could reproduce it with

emacs -Q -batch --eval '(let ((default-directory "/ssh::")) (expand-file-name 
"foo"))'

There is no related bug report; I've been pointed to this on #emacs of 
irc.freenode.net.

I believe I've fixed this, including a respective test in tramp-tests.el
for checks. But I'm wondering, whether the patch shall go into the
emacs-24 branch. It changes the autoload behaviour of Tramp, and cannot
be regarded as simple. And I believe the problem doesn't happen with
"normal" use of Emacs (whatever this is :-)

Comments? To be applied in emacs-24 or trunk?

Best regards, Michael.