bug#7513: 24.0.50; shell-command-default-error-buffer should always append to the bottom

[jidanni]

(info "(emacs) Single Shell") and
(describe-variable 'shell-command-default-error-buffer)
should mention that the errors accumulate in that buffer, and are not
wiped clean at each new command. Also mention they are separate by
form-feeds (^L).

Also the main reason I'm writing this bug report is currently
     `M-!' and `M-|' insert error output before point in that buffer.
But that often leads to jumbled output. They should always append to the
bottom! Like the view-echo-area-messages *Message* buffer.

Or have a variable for those who for some reason want output at a
different position, but bottom should be the default.
(emacs-snapshot package, version 1:20101120-1)