* lisp/calc/calc.el: Silence byte-compiler warnings

* lisp/calc/calc.el: Silence byte-compiler warnings

(calc-scan-for-dels): Use ignore-errors.
(calc-dispatch, calc-do-dispatch): Make unused arg optional.
(calc-read-key-sequence): Remove unused var `prompt2'.
(calc-kill-stack-buffer): Remove unused var `buflist'.
(calc): Remove unused var `oldbuf'.
(calc-refresh): Use inhibit-read-only.
(calc-can-abbrev-vectors): Declare.
(calc-record): Remove unused var `mainbuf'.
(math-sub-bignum): Remove unused var `sum'.
(math-svo-c, math-svo-wid, math-svo-off): Declare.