Bug in buffer-local-value

[Luc Teirlinck]

There is a bug in buffer-local-value, when used in connection with
defvaralias.  I believe that the ielm run below is self-explanatory.
The bug affects `C-h v" in a very confusing way.  I am insufficiently
familiar with the involved C code to fix this myself.

*** Welcome to IELM ***  Type (describe-mode) for help.
ELISP> (defvar aa 1)
aa
ELISP> (make-variable-buffer-local 'aa)
aa
ELISP> (defvaralias 'bb 'aa)
aa
ELISP> (setq bb 2)
2
ELISP> bb
2
ELISP> aa
2
ELISP> (buffer-local-value 'bb (current-buffer))
1      ;; Bug: should be 2
ELISP> (buffer-local-value 'aa (current-buffer))
2
ELISP> (local-variable-p 'bb)
t