(defcalcmodevar): New macro.

(defcalcmodevar): New macro.
(calc-mode-var-list-restore-default-values,
calc-mode-var-list-restore-saved-values): New functions.
(calc-mode-var-list): Use defcalcmodevar to define it.
(calc-always-load-extensions, calc-line-numbering)
(calc-line-breaking, calc-display-just, calc-display-origin)
(calc-number-radix, calc-leading-zeros, calc-group-digits)
(calc-group-char, calc-point-char, calc-frac-format)
(calc-prefer-frac, calc-hms-format, calc-date-format)
(calc-float-format, calc-full-float-format, calc-complex-format)
(calc-complex-mode, calc-infinite-mode, calc-display-strings)
(calc-matrix-just, calc-break-vectors, calc-full-vectors)
(calc-full-trail-vectors, calc-vector-commas, calc-vector-brackets)
(calc-matrix-brackets, calc-language, calc-language-option)
(calc-left-label, calc-right-label, calc-word-size)
(calc-previous-modulo, calc-simplify-mode, calc-auto-recompute)
(calc-display-raw, calc-internal-prec, calc-angle-mode)
(calc-algebraic-mode, calc-incomplete-algebraic-mode)
(calc-symbolic-mode, calc-matrix-mode, calc-shift-prefix)
(calc-window-height, calc-display-trail, calc-show-selections)
(calc-use-selections, calc-assoc-selections, calc-display-working-message)
(calc-auto-why, calc-timing, calc-mode-save-mode)
(calc-standard-date-formats, calc-autorange-units, calc-was-keypad-mode)
(calc-full-mode, calc-user-parse-tables, calc-gnuplot-default-device)
(calc-gnuplot-default-output, calc-gnuplot-print-device)
(calc-gnuplot-print-output, calc-gnuplot-geometry)
(calc-graph-default-resolution, calc-graph-default-resolution-3d)
(calc-invocation-macro, calc-show-banner): Use defcalcmodevar to
declare them and set their default values.