Cleanup some of EIEIO's namespace.

Cleanup some of EIEIO's namespace.
* lisp/emacs-lisp/eieio.el (eieio--define-field-accessors): New macro.
Use it to define all the class-* and object-* field accessors (renamed
to eieio--class-* and eieio--object-*).  Update all uses.
(eieio--class-num-slots, eieio--object-num-slots): Rename from
class-num-slots and object-num-slots.
(eieio--check-type): New macro.
(eieio-defclass, eieio-oref, eieio-oref-default, same-class-p)
(object-of-class-p, child-of-class-p, object-slots, class-slot-initarg)
(eieio-oset, eieio-oset-default, object-assoc, object-assoc-list)
(object-assoc-list-safe): Use it.
(eieio-defclass): Tighten regexp.
(eieio--defmethod): Use `memq'.  Signal an error for unknown method kind.
Remove unreachable code.
(object-class-fast): Declare obsolete.
(eieio-class-name, eieio-object-name, eieio-object-set-name-string)
(eieio-object-class, eieio-object-class-name, eieio-class-parents)
(eieio-class-children, eieio-class-precedence-list, eieio-class-parent):
Rename from class-name, object-name, object-set-name-string,
object-class, object-class-name, class-parents, class-children,
class-precedence-list, class-parent; with obsolete alias.
(class-of, class-direct-superclasses, class-direct-subclasses):
Declare obsolete.
(eieio-defmethod): Use `memq'; remove unreachable code.
* lisp/emacs-lisp/eieio-base.el (eieio-persistent-read):
* lisp/emacs-lisp/eieio-opt.el (eieio-class-button, eieio-describe-generic)
(eieio-browse-tree, eieio-browse): Use eieio--check-type.