(math-read-big-lines): New variable.

(math-read-big-lines): New variable.
(math-read-big-rec, math-read-big-char, math-read-big-emptyp)
(math-read-big-error, math-read-big-balance): Replace variable
lines by declared variable.

(math-read-big-baseline, math-read-big-h2): New variables.
(math-read-big-rec): Replace variables the-baseline and the-h2
by declared variables.

(math-read-big-rec): Fix typo.

(math-read-big-balance): Replace unbound variable by value.

(math-rb-h1, math-rb-h2, math-rb-v1, math-rb-v2): New variables.
(math-read-big-rec, math-read-big-char, math-read-big-emptyp)
(math-read-big-balance): Replace variables h1, h2, v1 and v2 by
declared variables.

(math-read-big-err-msg): New variable.
(math-read-big-error): Replace variable err-msg by declared variable.