Backport Tramp changes from trunk.

* net/tramp-adb.el (tramp-adb-sh-fix-ls-output): Use `bolp'.
(tramp-adb-handle-write-region): Improve messages.
(tramp-adb-maybe-open-connection): Don't set
`tramp-current-*' variables.

* net/tramp-cache.el (tramp-flush-file-function): Simplify check.
Suppress debug messages.

* net/tramp-ftp.el (top): Remove special handling for URL syntax.
(tramp-ftp-file-name-handler):

* net/tramp-gvfs.el (tramp-gvfs-methods) <sftp>: Add.
(tramp-gvfs-methods-mounttracker)
(tramp-gvfs-mountlocation-signature): Check `tramp-gvfs-enabled'
during initialization. 
(tramp-gvfs-handle-delete-file): Flush file properties, not
directory properties.
(tramp-gvfs-handle-file-attributes): Use `string-to-number' when
reading "unix::mode".
(tramp-gvfs-handle-file-name-all-completions):
Use "-h" option for "gvfs-ls".
(tramp-gvfs-url-file-name): Apply `cons' where appropriate.
`user' and `localname' could be nil.
(tramp-gvfs-send-command): Simplify traces.

* net/tramp-sh.el (vc-handled-backends, vc-bzr-program)
(vc-git-program, vc-hg-program): Declare.
(tramp-methods) <sftp>: Remove.  It has never worked satisfactorily.
(tramp-methods) <nc>: Add new method.
(tramp-methods) <telnet>: Redirect stderr to "/dev/null".
(tramp-methods) <plink, plinkx, pscp, psftp>: Improve
`tramp-login-args'.
(tramp-default-user-alist): Add "nc".
(top): Remove completion function for "sftp".  Add completion
functions for "nc" and "psftp".
(tramp-sh-handle-set-visited-file-modtime):
(tramp-sh-handle-verify-visited-file-modtime): Use `point-at-eol'.
(tramp-do-copy-or-rename-file-out-of-band):
Use cached "remote-copy-args" value, if available.  (Bug#18199)
Tweak docstring.  Implement support for "nc" method.
(tramp-sh-handle-expand-file-name, tramp-local-coding-commands)
(tramp-remote-coding-commands, tramp-call-local-coding-command):
Tweak docstring.
(tramp-sh-handle-start-file-process): Expand `default-directory'.
(tramp-sh-handle-write-region): Tweak error message.
(tramp-sh-handle-vc-registered): Remove backends when the remote
binary does not exist.
(tramp-open-connection-setup-interactive-shell):
Prefer utf-8 coding.  (Bug#17859)
(tramp-find-inline-encoding): Do not raise an error.
(tramp-make-copy-program-file-name): Tweak docstring.  Handle also
the "nc" case.  Quote result also locally.
(tramp-get-remote-id): Check also for "gid".
(tramp-get-remote-python):

* net/tramp-smb.el (tramp-smb-handle-copy-directory)
(tramp-smb-handle-set-file-acl): Use `start-process'.
(tramp-smb-handle-insert-directory): Use progress reporter.
(tramp-smb-handle-rename-file): Flush also file properties of
FILENAME.

* net/tramp.el (tramp-methods): Tweak docstring.
(tramp-file-name-handler): Apply `cons' where appropriate.
(tramp-handle-file-accessible-directory-p): Check for
`file-readable-p' instead of `file-executable-p'.
(tramp-handle-shell-command): Use `display-buffer'.  (Bug#18326)
(tramp-handle-unhandled-file-name-directory): Return "/".
(tramp-check-cached-permissions):
Use `tramp-compat-file-attributes'.
(tramp-call-process): Add new argument VEC.  Adapt callees in all
tramp*.el files.

* net/trampver.el: Update release number.