Remove obarrays

Remove obarrays

* lisp/emacs-lisp/eldoc.el (eldoc-message-commands): Make a package
instead of an obarray-vector.
* src/doc.c (Fsnarf_documentation): Don't use oblookup.
* src/eval.c (Fsignal): Debuggin helper code.
* src/font.c (font_intern_prop):  Don't use oblookup.
* src/lisp.h (intern_c_string): Delete inline function, use the one
in fread.c.
* src/lread.c: Remove everything realted to obarray, except Vobarray,
which is now set to Vemacs_package.
* src/minibuf.c (Ftry_completion, Fall_completions, Ftest_completion):
Accept packages.
* src/pkg.c: Adapted to other changes.