gnulib.mk (stddef.h): Sync with the latest change in lib/gnulib.mk.
emacs-lisp/package.el (package--list-loaded-files): New function

List files in a given directory which correspond to already loaded
files.
emacs-lisp/package.el (package-activate-1): Reload package after upgrade

After installing a package, reloads files returned by
`package--list-loaded-files'.
Fix bug#10125, bug#18443, and bug#18448.
directory-files-recursively symlink fix

* files.el (directory-files-recursively): Really check whether
files are symlinks.
Implement a new function `directory-name-p'

* doc/lispref/files.texi (Relative File Names): Mention
`directory-name-p'.

* etc/NEWS: Mention directory-name-p.

(directory-name-p): New function.
(directory-files-recursively): Use it.