update-autoloads can fail to find correct loaddefs.el

[lawrence mitchell <wence@gmx.li>]

In GNU Emacs 21.2.1 (i386-msvc-windows98.2222)
 of 2002-03-19 on buffy
configured using `configure --with-msvc (12.00)'


Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

I think this applies to all systems, however, have only tested on MS
Windows.
When calling update-autoloads the file name for loaddefs.el is the
value thereof at Emacs' build time, rather than where Emacs might
currently be installed.

The problem seems to lie in the fact that update-autoloads tries to
find loaddefs.el by doing:

(expand-file-name generated-autoload-file
                  (expand-file-name "lisp"
			            source-directory))

Which, if Emacs has subsequently moved, or been compiled in one
directory and then installed in another will return the wrong file
name.  I suppose this can be remedied at the user end by redefining
what source-directory's value is, but this doesn't seem like a nice
solution.  I'm not sure whether replacing that call by
(locate-library generated-autoload-file) would break anything.

-- 
lawrence mitchell <wence@gmx.li>