Merge from origin/emacs-26

11bd8aa24b Fix flymake's loading of subr-x
b500e06f4d Fix Bug#28896
d815de017b Skip a Flymake test for old gcc versions
fd3d8610b2 Make :align-to account for display-line-numbers
831eafc8ae Augment Flymake API for third-party extensions
ddd547fada Improve treatment of Fortran's "class default"
234b1e3864 Flymake backends must check proc obsoleteness in source bu...
3ea6a4d4ba Skip an rsync test in tramp-tests.el
25f83fa7c5 ; Indentation fixes
4d578d432d On Windows default a frame's border width to zero (Bug#28873)
6f1dea5c74 Spelling fixes
b8433b0954 Use pop-to-buffer-same-window instead of switch-to-buffer
2f7163fb72 Fix the MSDOS build.
2551d28fe8 Fix line number display after 'widen'
dc8812829b Remove resizable attribute on macOS undecorated frames (bu...
b970a4a52a Fix handling of `border-width' in `frameset--restore-frame...
445e92658f Mention how to send CC to > 1 address in a bug report
8ca6fa585a Improve format-time-string doc
2e1b3522b8 Improve documentation of 'line-number-display-width'
5b6e59cfdb Implement vc-default-dir-extra-headers for vc-rcs
22adeca42a In NEWS give advice on use of `switch-to-buffer' (Bug#28645)
2c3e6f1ddc Dont update primary selection with winner-undo
b38724ab67 Work around ImageMagick bug 825
20cc68e871 Document rectangle-preview option more (Bug#27974)
a0b7b301dd Do not reject https://gnu.org in commit messages
fb4200a875 Fix Edebug spec for cl-defun (bug#24255)
db68cefe72 Fix errors in kmacro.el post-command-hook
c63b344c3d Fix range-error in image-dired.el
081d2187c4 Fix 'line-number-display-width' in hscrolled windows
16e85456e7 Fix error in tramp-smb-handle-insert-directory
613db8d35c Don't reject PBM header whitespace unnecessarily
3205b12a78 Fix regression in display of PPM images
1ca9ae7069 Require subr-x when compiling nnimap.el
de60992053 Fix ert-test finding by symbol (Bug#28849)
51615a8082 Don't remember old debugger window (Bug#17882)
5980de3727 Disable python native completion on w32 (Bug#28580)
616b4c5956 Let select-frame-by-name choose any frame when called from...
8eb3c01dbd * lisp/dired-aux.el (dired-create-directory): Doc fix.
325dfdae13 Avoid compilation warnings in optimized builds
f79382819c ; * src/composite.c (Fclear_composition_cache): Fix last c...
f95cd5cd70 Improve customization of arabic-shaper-ZWNJ-handling.
a7f154688d Improve customization type of 'mouse-drag-and-drop-region'
864734d112 ; Prefer https: to http: in GNU URLs
3c78960a47 Encourage https: in commit messages
def9715282 ; Cleanup of etc/NEWS
4e59ecc646 Fix wording in Elisp manual's child frames section (Bug#28...
eda9f5018c Another fix for C mode fontification of w32 source files
05aadd8990 Fix fontification of ALIGN_STACK functions
aa0c38f358 Make sure thread stack is properly aligned on MS-Windows
d7038020aa Do not under-align pseudovectors
ff33053012 Fix indentation bug in multi-line CSS selectors
8968be822e ; * etc/NEWS: Grammar and spelling fixes
716b84034d gnutls_mac_get_nonce_size has been added in gnutls 3.3
55e313f7be ; * CONTRIBUTE: More suggestions for using US English.
622c675648 * CONTRIBUTE: Suggest American English.

# Conflicts:
#	etc/NEWS
#	msdos/sed2v2.inp

lisp/emacs-lisp/debug.el

@@ -253,7 +253,9 @@ first will be printed into the backtrace buffer."
 		;; Unshow debugger-buffer.
 		(quit-restore-window debugger-window debugger-bury-or-kill)
 		;; Restore current buffer (Bug#12502).
-		(set-buffer debugger-old-buffer))))
+		(set-buffer debugger-old-buffer)))
+            ;; Forget debugger window, it won't be back (Bug#17882).
+            (setq debugger-previous-window nil))
           ;; Restore previous state of debugger-buffer in case we were
           ;; in a recursive invocation of the debugger, otherwise just
           ;; erase the buffer and put it into fundamental mode.