fix parsing of block comments with unicode characters

[JZYFC]

This PR attemps to fix #315

[wetneb]

Ah, thanks! You found another bunch of char references that I forgot to replace in my fix. Would you mind making a follow-up PR on tree-sitter-rust-orchard?

[JZYFC]

Ah, thanks! You found another bunch of char references that I forgot to replace in my fix. Would you mind making a follow-up PR on tree-sitter-rust-orchard?

I appreciate your work with tree-sitter-rust-orchard. You can just fix these yourself. I'm OK with that.