before their first use. Use `when', `unless'. Remove trailing
periods from error forms. Add description and headers suggested by
Emacs Lisp coding conventions.
(calc-do-quick-calc): Use `frame-width' instead of `screen-width'.
(calcAlg-edit): Use `minibuffer-contents' instead of `buffer-string'.
(calcAlg-enter): Likewise.
(calcAlg-enter): Use `minibuffer-prompt-end' instead of `point-min'.