bug#9030: `where-is' doesn't play well `with with-output-to-string'

[PJ Weisberg]

This expression:

(with-output-to-string
  (where-is 'yank))

returns nil, and prints a message in the echo area.  This one-line
change fixes it:

diff --git a/lisp/help.el b/lisp/help.el
index e6496f6..53e99e7 100644
--- a/lisp/help.el
+++ b/lisp/help.el
@@ -527,7 +527,7 @@ If INSERT (the prefix arg) is non-nil, insert the
message in the buffer."
   (unless definition (error "No command"))
   (let ((func (indirect-function definition))
         (defs nil)
-        (standard-output (if insert (current-buffer) t)))
+        (standard-output (if insert (current-buffer) standard-output)))
     ;; In DEFS, find all symbols that are aliases for DEFINITION.
     (mapatoms (lambda (symbol)
                (and (fboundp symbol)