Ange-FTP integration

[Michael Albinus]

Hello,

I've committed some large changes to tramp.el in CVS. The major change
is that Ange-FTP integration is encapsulated now in a module called
tramp-ftp.el.

The motivation for that change is two-folded:

- Ange-FTP has been interconnected heavily with Tramp. This was not a
  clean interface, and it was a burden to possibly integrate EFS. I
  have no idea whether EFS will cooperate ever with Tramp; but from
  the interface point of view it will be simpler now.

- FTP is now regarded as a "foreign" method. That means, it is a
  method implemented outside tramp.el. This will ease the integration
  of other "foreign" methods, like "smb" (what I do plan next time).

Please do report any degradation in integration of Ange-FTP. Although
heavily tested, I cannot guarantee it will work under all
circumstances. Of course.

Btw, if you have a better wording for "foreign method" please tell
me. "external method" is used already, and my English isn't tough
enough to improve.