scribble: CSS repairs & clean-up toward documentation of class names
racket/gui docs: use 'compact style for some itemizations
box-cas!: less JIT-generated work if the boolean result is ignored
Remove units in parts of `compiler`, `dynext`, `setup` and create the `cext-lib` package.

`cext-lib` contains much of the contents of `dynext`, which
is no longer very widely used.

Also moved the implementation of the `mzc` executable
to a more appropriate package.

Also, used `lazy-require` consistently for dynamically
loading implementations.
Fix dynamic loading of parameters in `mzc`.
fix bitmap printing in the teaching languages

closes PR 14049
Add an .htaccess symlink to the toplevel of the irc-logs directory.

This allows redirection configuration (for old links) and access control
be done directly in the irc-logs directory.
slideshow: more efficient `bitmap`

Use bitmap with alpha, instead of with mask.
racket/draw: faster `draw-bitmap` when alpha < 1.0

In common cases, use Cairo's alpha support instead of cloning the
bitmap to apply an alpha.
slideshow: always clip drawing to slide area
slideshow: fix tutorial show