Respect text-quoting-style in calc

Respect text-quoting-style in calc

In calc, tespect text-quoting-style preference in diagnostic
formats and fix a few similar problems in docstrings.
* lisp/calc/calc-aent.el (math-read-factor):
* lisp/calc/calc-embed.el (calc-do-embedded):
* lisp/calc/calc-ext.el (calc-user-function-list)
* lisp/calc/calc-graph.el (calc-graph-show-dumb):
* lisp/calc/calc-help.el (calc-describe-key)
(calc-describe-thing):
* lisp/calc/calc-lang.el (calc-c-language)
(math-parse-fortran-vector-end, math-parse-tex-sum)
(math-parse-eqn-matrix, math-parse-eqn-prime)
(calc-yacas-language, calc-maxima-language, calc-giac-language)
(math-read-big-rec, math-read-big-balance):
* lisp/calc/calc-mode.el (calc-auto-why, calc-save-modes)
(calc-auto-recompute):
* lisp/calc/calc-prog.el (calc-user-define-invocation)
(math-do-arg-check):
* lisp/calc/calc-store.el (calc-edit-variable):
* lisp/calc/calc-units.el (math-build-units-table-buffer):
* lisp/calc/calc-vec.el (math-read-brackets):
* lisp/calc/calc-yank.el (calc-edit-mode):
* lisp/calc/calc.el (calc, calc-do, calc-user-invocation):
Use curved quotes in diagnostic format strings.
* lisp/calc/calc-help.el (calc-describe-thing):
Format docstrings with substitute-command-keys.
* lisp/calc/calc-help.el (calc-j-prefix-help):
* lisp/calc/calc-misc.el (calc-help):
* lisp/calc/calc-ext.el (calc-shift-Z-prefix-help):
Escape a docstring "`".