(htmlfontify-load-rgb-file): Remove unnused var `ff'.
Use with-current-buffer and string-to-number.
(hfy-fallback-colour-values): Use assoc-string.
* htmlfontify.el (hfy-face-to-css): Remove unused var `style'.
(hfy-face-at): Remove unused var `found-face'.
(hfy-compile-stylesheet): Remove unused var `css'.
(hfy-fontify-buffer): Remove unused vars `in-style', `invis-button',
and `orig-buffer'.
(hfy-buffer, hfy-copy-and-fontify-file, hfy-parse-tags-buffer):
Use with-current-buffer.
(hfy-text-p): Use expand-file-name and fewer setq.
