Merge from origin/emacs-26

1d732d6 (origin/emacs-26) Fix gud-statement for pdb
91a68b5 ; * msdos/INSTALL: Add info about GCC versions.
7ddcc9a Document 'custom-group'
58f9e15 A minor addition to etc/DEBUG
4590414 Avoid errors in ispell.el when Enchant returns empty extra chars
d0d75f9 Make 'ispell-initialize-spellchecker-hook' work again
b90ce66 Handle selected_window change in prepare_menu_bars (Bug#31312)
79ad0b3 ; * INSTALL: Fix Emacs version number.  (Bug#31358)
91de88b Fix report-emacs-bug via mailclient on MS-Windows
f4b5ff2 Port collation tests to glibc 2.27

3 files changed, 24 insertions, 5 deletions

diff --git a/lisp/net/browse-url.el b/lisp/net/browse-url.el
index bdedcb2bd3e..bf179c8782a 100644
--- a/lisp/net/browse-url.el
+++ b/lisp/net/browse-url.el
@@ -877,7 +877,21 @@ The optional NEW-WINDOW argument is not used."
            (error "Browsing URLs is not supported on this system")))
         ((eq system-type 'cygwin)
          (call-process "cygstart" nil nil nil url))
-        (t (w32-shell-execute "open" (url-unhex-string url)))))
+        (t
+         (w32-shell-execute "open"
+                            ;; w32-shell-execute passes file:// URLs
+                            ;; to APIs that expect file names, so we
+                            ;; need to unhex any %nn encoded
+                            ;; characters in the URL.  We don't do
+                            ;; that for other URLs; in particular,
+                            ;; default Windows mail client barfs on
+                            ;; quotes in the MAILTO URLs, so we prefer
+                            ;; to leave the URL with its embedded %nn
+                            ;; encoding intact.
+                            (if (eq t (compare-strings url nil 7
+                                                       "file://" nil nil))
+                                (url-unhex-string url)
+                              url)))))
 
 (defun browse-url-default-macosx-browser (url &optional _new-window)
   "Invoke the macOS system's default Web browser.
diff --git a/lisp/progmodes/gud.el b/lisp/progmodes/gud.el
index 2664d03e723..de398350bd2 100644
--- a/lisp/progmodes/gud.el
+++ b/lisp/progmodes/gud.el
@@ -1695,8 +1695,7 @@ and source-file directory for your debugger."
   (gud-def gud-up     "up"           "<" "Up one stack frame.")
   (gud-def gud-down   "down"         ">" "Down one stack frame.")
   (gud-def gud-print  "p %e"         "\C-p" "Evaluate Python expression at point.")
-  ;; Is this right?
-  (gud-def gud-statement "! %e"      "\C-e" "Execute Python statement at point.")
+  (gud-def gud-statement "!%e"      "\C-e" "Execute Python statement at point.")
 
   ;; (setq comint-prompt-regexp "^(.*pdb[+]?) *")
   (setq comint-prompt-regexp "^(Pdb) *")
diff --git a/lisp/textmodes/ispell.el b/lisp/textmodes/ispell.el
index d03d12b3758..73a2c2da8b1 100644
--- a/lisp/textmodes/ispell.el
+++ b/lisp/textmodes/ispell.el
@@ -1212,8 +1212,10 @@ Internal use.")
 (defun ispell--get-extra-word-characters (&optional lang)
   "Get the extra word characters for LANG as a character class.
 If LANG is omitted, get the extra word characters for the default language."
-  (concat "[" (string-trim-right (apply 'ispell--call-enchant-lsmod
-                                        (append '("-word-chars") (if lang `(,lang))))) "]"))
+  (let ((extra (string-trim-right
+                (apply 'ispell--call-enchant-lsmod
+                       (append '("-word-chars") (if lang `(,lang)))))))
+    (if (string= extra "") "" (concat "[" extra "]"))))
 
 (defun ispell-find-enchant-dictionaries ()
   "Find Enchant's dictionaries, and record in `ispell-enchant-dictionary-alist'."
@@ -1243,6 +1245,10 @@ If LANG is omitted, get the extra word characters for the default language."
 (defvar ispell-last-program-name nil
   "Last value of `ispell-program-name'.  Internal use.")
 
+;; Allow dynamically binding ispell-base-dicts-override-alist as
+;; advertised in the doc string of ispell-initialize-spellchecker-hook.
+(defvar ispell-base-dicts-override-alist)
+
 (defvar ispell-initialize-spellchecker-hook nil
   "Normal hook run on spellchecker initialization.
 This hook is run when a spellchecker is used for the first