https://github.com/minetest/minetest/pull/10100
has introduced a few inconsistencies with the formats of previous texture modifiers:
`[fill` is the first texture modifier to have a modifying and a generating variant.
Thus `texmod` "constructors" and `texmod` "modifiers" / methods had to be separated;
`texmod.fill` is not the same as `tm.fill` where `tm` is `texmod` instance.
It is rather dirty that the generating variant would ignore
extraneous parameters of the modifying variant, so this is not replicated by the parser.
`[hsl`, `[colorizehsl`, `[contrast` and `[screen` are pretty standard texture modifiers
as far as the DSL is concerned. `[hsl` and `[colorizehsl` are very similar.
`[hardlight` is the first texture modifier to exist just for swapping the base and parameter.
`a^[overlay:b` and `b^[hardlight:a` are both normalized to `b:[hardlight:a` by the DSL.
`[overlay` (called "overlay blend" in the docs) creates a naming conflict with
literal overlaying (`^`). This is resolved by renaming `:overlay` to `:blit`.
