We need to make sure the \put command arguments will expand to a
(fractional) number, so \strip@pt is added, and the \dimexpr properly
closed with \relax

Explain non-standard encoding in LatinRules.xdy

In order to fulfill its function, LatinRules.xdy must use single,
non-standard byte characters (neither ASCII, nor multi-byte UTF-8).
To someone encountering the file without knowing its purpose (e.g.
due a post-processing raising a warning for the unrecognized encoding)
this is likely surprising, and may seem like a holdover from a time where
Unicode wasn't as universally supported.

The added comment should make clear that the file must stay as it is,
and in particular that it must not be "standardized" to UTF-8.

- LaTeX: box padding (t,r,b,l), borders (t,r,b,l), shadows (x,y) or radii

- LaTeX: fix #10650 via usage of our own sophisticated \fcolorbox

- LaTeX: user interface via 'sphinxsetup' to enhanced code-blocks frames

- LaTeX: user interface via 'sphinxsetup' to enhanced topic boxes

- LaTeX: CSS-named-alikes 'sphinxsetup' options for code-blocks and
  topics

- LaTeX: CSS-named-alikes 'sphinxsetup' keys for warning type notices
  (fix #10651)

- LaTeX: documentation of the new CSS-like options

- LaTeX: remove #10619 documentation, as the #10619 added
  shadowBorderColor and shadowShadowColor now named respectively:

  aside.topic_border-TeXcolor and aside.topic_box-shadow-TeXcolor

- LaTeX: use div.topic option prefix and not aside.topic for CSS-like
  options

- LaTeX: keep the implicit legacy padding of warning type boxes as
  default behaviour

LaTeX: optional rounded corners for framing of code-blocks