Handle --version reasonably in CANNOT_DUMP configuration.

Handle --version reasonably in CANNOT_DUMP configuration.

* src/emacs.c (emacs_version, emacs_copyright): New string
variables.
(Vemacs_version, Vemacs_copyright): New Lisp_Object variables.
(syms_of_emacs): Defvar them, and initialize them from the C
string variables.
(main): If initialization hasn't been done, print initial version
info from the C strings, instead of starting an interactive session.
* lisp/version.el (emacs-copyright, emacs-version): Don't define
here.
* configure.in: Look for version string in its new place.