Avoid recursive load of tramp.el

Avoid recursive load of tramp.el

* net/tramp.el (tramp-run-real-handler, tramp-file-name-handler):
Do not autoload.
(tramp-file-name-handler, tramp-completion-file-name-handler):
Revert patch from 2014-04-10, it isn't necessary anymore.
(tramp-autoload-file-name-handler)
(tramp-register-autoload-file-name-handlers): New defuns.
(top): Autoload call of `tramp-register-autoload-file-name-handlers'.
(tramp-register-file-name-handlers): Remove also
`tramp-autoload-file-name-handler' from `file-name-handler-list'.
Do not autoload its invocation, but eval it after loading of 'tramp.

* net/tramp-adb.el (tramp-unload-hook): Unload `tramp-adb'.

* net/tramp-compat.el (tramp-unload-hook): Unload `tramp-loaddefs'.