* Don't lowercase element names and attribute names in selectors
https://www.w3.org/TR/css3-selectors/#casesens
> All Selectors syntax is case-insensitive within the ASCII range (i.e.
> [a-z] and [A-Z] are equivalent), except for parts that are not under the
> control of Selectors. The case sensitivity of document language element
> names, attribute names, and attribute values in selectors depends on the
> document language. For example, in HTML, element names are
> case-insensitive, but in XML, they are case-sensitive.
Fixes#3304.
* Fix number normalization in selector interpolation
Fixes#2820. While that issue is about `@media (--fooBar)` in
particular, this commit changes to never lowercase stuff starting with
`--` in general, as it seems like those `--customStuff` things can pop
up kind of anywhere.
Evilebot Tnawi