calc.el, calc-(ext|poly), calccomp: Use lexical-binding

calc.el, calc-(ext|poly), calccomp: Use lexical-binding

* lisp/calc/calc-ext.el: Use lexical-binding, silence warnings.
(calc-init-extensions): Remove a few functions which can't be called
directly since they depend on dynamically scoped vars.
(calc-embedded-quiet): Declare.
(math-defcache): Use 'declare'.
(math-normalize-a): Remove declaration.
(math-normalize-nonstandard): Receive 'a' as arg instead.
(math-defintegral): Use 'declare'.
(math-exp-pos, math-exp-old-pos, math-exp-keep-spaces, math-rb-h2)
(math-read-big-baseline, math-read-big-h2, math-read-big-err-msg)
(math-exp-token, math-expr-data, math-exp-str): Declare.
(math-map-tree, math-read-expr): Avoid dynvars as formal arguments.

* lisp/calc/calc-poly.el: Use lexical-binding, silence warnings.
Turn some comments into docstrings.
(math-poly-div): Avoid dynvars as formal arguments.
(math-poly-base-top-expr): Move declaration before first use.
(calcFunc-factors, math-factor-expr, math-factor-expr-try)
(calcFunc-factor): Avoid dynvars as formal arguments.

* lisp/calc/calc.el: Use lexical-binding, silence warnings.
(math-normalize-a): Remove.
(math-normalize): Use lexical var 'a' instead.
(math-svo-c): Remove.
(math-stack-value-offset): Pass 'c' explicitly as arg to
math-stack-value-offset-fancy instead.

* lisp/calc/calccomp.el: Use lexical-binding, silence warnings.
(math-svo-c): Remove.
(math-stack-value-offset-fancy): Use new arg 'c' instead.
(math-comp-to-string-flat): Avoid dynvars as formal arguments.