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, 2 deletions

diff --git a/doc/lispref/objects.texi b/doc/lispref/objects.texi
index 4be2eb6918b..4242223a48e 100644
--- a/doc/lispref/objects.texi
+++ b/doc/lispref/objects.texi
@@ -2336,8 +2336,12 @@ same sequence of character codes and all these codes are in the range
 @end group
 @end example
 
-However, two distinct buffers are never considered @code{equal}, even if
-their textual contents are the same.
+The @code{equal} function recursively compares the contents of objects
+if they are integers, strings, markers, vectors, bool-vectors,
+byte-code function objects, char-tables, records, or font objects.
+Other objects are considered @code{equal} only if they are @code{eq}.
+For example, two distinct buffers are never considered @code{equal},
+even if their textual contents are the same.
 @end defun
 
   For @code{equal}, equality is defined recursively; for example, given