bug#3463: 23.0.94; describe-variable misses buffer local value for long outputs

describe-variable overwrites its own input when showing the value of a
buffer local variable that has a default value with long output. To
show this start from "emacs -Q" and in *scratch* write

  (set (make-local-variable 'auto-mode-alist) nil)

and eval it. Then show the value of auto-mode-alist in *scratch* with
describe-variable.




In GNU Emacs 23.0.94.1 (i386-mingw-nt5.1.2600)
 of 2009-05-23
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --no-opt --cflags
-Ic:/g/include -fno-crossjumping'