Make `rustc_lexer::cursor::Cursor` public.

`Cursor` is currently hidden, and the main tokenization path uses
`rustc_lexer::first_token` which involves constructing a new `Cursor`
for every single token, which is weird. Also, `first_token` also can't
handle empty input, so callers have to check for that first.

This commit makes `Cursor` public, so `StringReader` can contain a
`Cursor`, which results in a simpler structure. The commit also changes
`StringReader::advance_token` so it returns an `Option<Token>`,
simplifying the the empty input case.

0 files changed, 0 insertions, 0 deletions