Prefer ?* to hide passwords

It might be argued that a hidden string is more legible when using
?* as the hidden character instead of ?.
For example, the following strings have the same length:
"......"

"******"

It's slighly easier to visually count the number of characters in the second
string (Bug#32220).

* lisp/subr.el (read-passwd): Prefer ?* as default char instead of ?.
* doc/lispref/minibuf.texi (Reading a Password): Update manual.
; * etc/NEWS (Changes in Emacs 27.1): Announce the change.

doc/lispref/minibuf.texi

@@ -2199,7 +2199,7 @@ function @code{read-passwd}.
 @defun read-passwd prompt &optional confirm default
 This function reads a password, prompting with @var{prompt}.  It does
 not echo the password as the user types it; instead, it echoes
-@samp{.}  for each character in the password.  If you want to apply
+@samp{*}  for each character in the password.  If you want to apply
 another character to hide the password, let-bind the variable
 @code{read-hide-char} with that character.
 

etc/NEWS

@@ -92,6 +92,9 @@ the new version of the file again.)
 
 * Changes in Emacs 27.1
 
++++
+** The function 'read-passwd' uses '*' as default character to hide passwords.
+
 ---
 ** New variable 'xft-ignore-color-fonts'.
 Default t means don't try to load color fonts when using Xft, as they

lisp/subr.el

@@ -2299,7 +2299,7 @@ some sort of escape sequence, the ambiguity is resolved via `read-key-delay'."
 If optional CONFIRM is non-nil, read the password twice to make sure.
 Optional DEFAULT is a default password to use instead of empty input.
 
-This function echoes `.' for each character that the user types.
+This function echoes `*' for each character that the user types.
 You could let-bind `read-hide-char' to another hiding character, though.
 
 Once the caller uses the password, it can erase the password
@@ -2325,7 +2325,7 @@ by doing (clear-string STRING)."
                                      beg)))
              (dotimes (i (- end beg))
                (put-text-property (+ i beg) (+ 1 i beg)
-                                  'display (string (or read-hide-char ?.))))))
+                                  'display (string (or read-hide-char ?*))))))
           minibuf)
       (minibuffer-with-setup-hook
           (lambda ()
@@ -2340,7 +2340,7 @@ by doing (clear-string STRING)."
             (add-hook 'after-change-functions hide-chars-fun nil 'local))
         (unwind-protect
             (let ((enable-recursive-minibuffers t)
-		  (read-hide-char (or read-hide-char ?.)))
+		  (read-hide-char (or read-hide-char ?*)))
               (read-string prompt nil t default)) ; t = "no history"
           (when (buffer-live-p minibuf)
             (with-current-buffer minibuf