Extend memory-info for remote systems

* doc/lispref/files.texi (Magic File Names): Add memory-info.

* doc/lispref/internals.texi (Garbage Collection): memory-info can
also retrieve values from remote systems.

* etc/NEWS: Document changes in memory-info.  Fix typos.

* lisp/files.el (warn-maybe-out-of-memory): Ensure local memory info.

* lisp/net/tramp.el (tramp-handle-memory-info): New defun.
(tramp-file-name-for-operation)
* lisp/net/tramp-adb.el (tramp-adb-file-name-handler-alist):
* lisp/net/tramp-archive.el (tramp-archive-file-name-handler-alist):
* lisp/net/tramp-crypt.el (tramp-crypt-file-name-handler-alist):
* lisp/net/tramp-gvfs.el (tramp-gvfs-file-name-handler-alist):
* lisp/net/tramp-rclone.el (tramp-rclone-file-name-handler-alist):
* lisp/net/tramp-sh.el (tramp-sh-file-name-handler-alist):
* lisp/net/tramp-smb.el (tramp-smb-file-name-handler-alist):
* lisp/net/tramp-sshfs.el (tramp-sshfs-file-name-handler-alist)
* lisp/net/tramp-sudoedit.el (tramp-sudoedit-file-name-handler-alist):
Add 'memory-info'.

* lisp/net/tramp-sshfs.el (tramp-sshfs-handle-exec-path):
Let-bind `process-file-side-effects'.

* src/alloc.c (Fmemory_info): Support remote systems.
(Qmemory_info): Declare.

* test/lisp/net/tramp-tests.el (tramp-test31-memory-info): New test.

1 files changed, 3 insertions, 0 deletions

diff --git a/doc/lispref/internals.texi b/doc/lispref/internals.texi
index 4640b6d7591..c4e724d761c 100644
--- a/doc/lispref/internals.texi
+++ b/doc/lispref/internals.texi
@@ -622,6 +622,9 @@ a certain kind of object.  See the documentation string for details.
 @defun memory-info
 This functions returns an amount of total system memory and how much
 of it is free.  On an unsupported system, the value may be @code{nil}.
+
+If @code{default-directory} points to a remote host, memory
+information of that host is returned.
 @end defun
 
 @defvar gcs-done