bug#690: 23.0.60; Function origin file misremembered

[martin rudalics]

> I do not see much value in abbreviating the file name at all; unless
> that is important for other features to work, I find that the original
> file name should be preserved in case of doubt. (symbol-file
> 'prolog-mode) correctly evaluates to "/Users/mt/prolog.el", so this is
> what should be shown. Otherwise, even future changes to load-path could
> lead to distorted file origins of functions that are already loaded.

`load-path' is fragile.  Consider the case where you have duplicates of
files foo.el and bar.el in two different directories that are both in
`load-path'.  You can't insist on finding foo.el in one and bar.el in
the other directory.  As I proposed in another thread we could try to
_always_ find the definition from `symbol-file' and use that from the
build directory iff the former fails.  This should handle your case as
well.

martin