Merge from origin/emacs-26

a87ce5c4b4 * src/lisp.h (GCALIGNED): Clarify comment (Bug#29040).
8a31e9993f ; etc/NEWS: Add cpp-message-min-time-interval.  (Bug#28961)
ac0bb9a192 Improve the doc of eshell-cmpl-* custom variables (Bug#25069)
36400c7dc9 Fix mouse-scrollbar offset on GNUstep and old macOS (bug#2...
04bc1410c2 Merge from Gnulib
6b08ad5263 Fix alignment portability problems
a9f8706fa8 Fix completion of colon after CSS property (Bug#29056)
9031dec527 ; * src/alloc.c (sweep_symbols): Fix last change.
fdd3dcfa4e * src/alloc.c (sweep_symbols): Tweak last change
27964af438 In frame parameters documentation mention desktop saving/r...
1bd4e7c243 ; Fix typo in ChangeLog.3
4182a60d31 Don't have frameset save the 'client' parameter (Bug#29067)
9d31a97092 ; Spelling fixes
460a25f212 Handle generic variables in cl-defgeneric Edebug spec
dc0a25c2f9 Give a more sensible message if file-attributes fails (Bug...
8453423c7c Avoid wrong value from file-attributes on Linux kernel bef...
70621e2571 Fix customization of debugger-print-function (Bug#29077)

# Conflicts:
#	etc/NEWS

lisp/emacs-lisp/debug.el

@@ -51,8 +51,9 @@ the middle is discarded, and just the beginning and end are displayed."
 
 (defcustom debugger-print-function #'cl-prin1
   "Function used to print values in the debugger backtraces."
-  :type 'function
-  :options '(cl-prin1 prin1)
+  :type '(choice (const cl-prin1)
+                 (const prin1)
+                 function)
   :version "26.1")
 
 (defcustom debugger-bury-or-kill 'bury