On my M1 mac this shows as ~25% faster at parsing Num.roc than the old implementation, probably because nobody wrote any NEON code.
Even on my x86_64 linux box (Ryzen 2700x), this shows as 10% faster than the current SSE implementation (running with RUSTFLAGS="-C target-cpu=native").
This removes the need to explicitly pass thru min_indent when using the parser combinators.
My ultimate goal here is to evolve the current parser closer toward a purely combinator-based parser,
at which point we can more easily transition smoothly to a formal(ish) grammar, or expand the meanings of combinators
to include things like:
* Incremental (re)parsing
* Unified parsing and formatting code
* Better error recovery
* Using the main parser directly for syntax highlighting
