Problem: Currently vim.hl.range only allows one timed highlight.
Creating another one, removes the old one.
Solution: vim.hl.range now returns a timer and a function. The timer
keeps track of how much time is left in the highlight and the function
allows you to clear it, letting the user decide what to do with old
highlights.
Problem: yi' don't highlight last character since
8ce504820a.
Solution: Always use `opts.inclusive=true`, since calculation of `"]`
(`b_op_end`) have taken `inclusive` into account.
Problem:
`vim.validate()` takes two forms when it only needs one.
Solution:
- Teach the fast form all the features of the spec form.
- Deprecate the spec form.
- General optimizations for both forms.
- Add a `message` argument which can be used alongside or in place
of the `optional` argument.
Problem:
- `vim.highlight` module does not follow `:help dev-name-common`, which
documents the name for "highlight" as "hl".
- Shorter names are usually preferred.
Solution:
Rename `vim.highlight` to `vim.hl`.
This is not a breaking change until 2.0 (or maybe never).
