Recent symbol-file changes vs. help functions

[Romain Francoise <romain@orebokech.com>]

A few days ago, load-history was changed to hold absolute file names
instead of library names.  `symbol-file' was subsequently changed to
return absolute file names, too.

Because of this, the output of `describe-function' differs depending on
whether the symbol is autoloaded or not because we use `symbol-file' in
the first case, and loaddefs.el in the other.

E.g.:

,----[ C-h f viper-mode RET ]
| viper-mode is an interactive autoloaded Lisp function in `viper'.
`----

,----[ C-h f ignore RET ]
| ignore is an interactive compiled Lisp function in `/home/romain/Work/Repos/Emacs/emacs/lisp/subr.elc'.
`----

There are probably other inconsistencies.  I think we should convert the
absolute file name back into a library name in help functions.

-- 
Romain Francoise <romain@orebokech.com> | I used to think there is no
it's a miracle -- http://orebokech.com/ | future left at all.