Fix sxhash-equal on bytecodes, markers, etc.

Problem reported by Pip Cet (Bug#38912#14).
* doc/lispref/objects.texi (Equality Predicates):
Document better when ‘equal’ looks inside objects.
* doc/lispref/windows.texi (Window Configurations):
Don’t say that ‘equal’ looks inside window configurations.
* etc/NEWS: Mention the change.
* src/fns.c (internal_equal):
Do not look inside window configurations.
(sxhash_obj): Hash markers, byte-code function objects,
char-tables, and font objects consistently with Fequal.
* src/window.c (compare_window_configurations):
Now static.  Remove last argument.  Caller changed.
* test/lisp/ffap-tests.el (ffap-other-window--bug-25352):
Use compare-window-configurations, not ‘equal’.
* test/src/fns-tests.el (test-sxhash-equal): New test.

1 files changed, 6 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index d6cabf8e9e4..0784160ce22 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -42,6 +42,12 @@ applies, and please also update docstrings as needed.
 
 * Incompatible Lisp Changes in Emacs 28.1
 
+** 'equal' no longer examines some contents of window configurations.
+Instead, it considers window configurations to be equal only if they
+are eq.  To compare contents, use compare-window-configurations
+instead.  This change helps fix a bug in sxhash-equal, which returned
+incorrect hashes for window configurations and some other objects.
+
 
 * Lisp Changes in Emacs 28.1