zmacs: move zlisp variable declarations to an appropriate file.

* lib/zmacs/zlisp/variables.zl (auto-fill-mode): Move from here...
* lib/zmacs/zlisp/buffer.zl (auto-fill-mode): ...to here.
* lib/zmacs/zlisp/variables.zl (ring-bell): Move from here...
* lib/zmacs/zlisp/edit.zl (ring-bell): ...to here.
* lib/zmacs/zlisp/variables.zl (make-backup-files)
(backup-directory): Move from here...
* lib/zmacs/zlisp/file.zl (make-backup-files, backup-directory):
...to here.
* lib/zmacs/zlisp/variables.zl (kill-whole-line): Move from
here...
* lib/zmacs/zlisp/killring.zl (kill-whole-line): ...to here.
* lib/zmacs/zlisp/variables.zl (indent-tabs-mode)
(tab-always-indent, tab-width, standard-indent, fill-column):
Move from here...
* lib/zmacs/zlisp/line.zl (indent-tabs-mode, tab-always-indent)
(tab-width, standard-indent, fill-column): ...to here.
* lib/zmacs/zlisp/variables.zl (case-fold-search, case-replace):
Move from here...
* lib/zmacs/zlisp/search.zl (case-fold-search, case-replace):
...to here.
* lib/zmacs/zlisp/variables.zl (highlight-nonselected-windows)
(transient-mark-mode): Move from here...
* lib/zmacs/zlisp/window.zl (highlight-nonselected-windows)
(transient-mark-mode): ...to here.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>