(texinfo-raisesections-alist, texinfo-lowersections-alist): Merge definition

(texinfo-raisesections-alist, texinfo-lowersections-alist): Merge definition
and declaration.
(texinfo-start-of-header, texinfo-end-of-header): Remove.
(texinfo-format-syntax-table): Merge init into declaration.
(texinfo-format-parse-line-args, texinfo-format-parse-args)
(texinfo-format-parse-defun-args, texinfo-format-node)
(texinfo-push-stack, texinfo-multitable-widths)
(texinfo-define-info-enclosure, texinfo-alias)
(texinfo-format-defindex, batch-texinfo-format): Use push.
(texinfo-footnote-number): Remove duplicate declaration.