Use make-directory handlers uniformly

Use make-directory handlers uniformly

Formerly, the code supported both make-directory and
make-directory-internal handlers. This led to confusion and meant than
in a few cases (nnmaildir, ido) remote directories could not be used in
some cases.  Fix this by using only make-directory handlers.

Perhaps there used to be a reason for why there were both
make-directory and make-directory-internal handlers, but whatever that
reason was, it seems to have vanished even before now.

There is no longer any need for make-directory-internal handlers, as
the few remaining callers that use make-directory-internal do so only
when there are no handlers.  However, this change keeps the existing
make-directory-internal handlers for now, in case this code is ever
used in older Emacs versions that still call those handlers.

* lisp/gnus/nnmaildir.el (nnmaildir--mkdir):
* lisp/ido.el (ido-file-internal):
* lisp/net/tramp-smb.el (tramp-smb-handle-make-directory):
Use make-directory, not make-directory-internal.
* lisp/net/tramp-smb.el (tramp-smb-handle-make-directory-internal):
Now obsolete.
* src/fileio.c (Fmake_directory_internal): Do not look for or
use a make-directory-internal handler.
* test/lisp/files-tests.el:
(files-tests-file-name-non-special-make-directory-internal):
Remove, as this test incorrectly assumes that make-directory-internal
must support handlers.