Between ffc5f1c, when grammar.md was created by copying parts of the
reference, and 8cf2552, when all EBNF was removed from reference.md,
there were parts of the grammar that were updated in reference.md but
not grammar.md, and then they weren't copied over because they existed
already, but they were slightly out of date.
Example: the `path_item : ident | "self" ;` rule in Use declarations was
changed from "mod" to "self" in the reference in 195fd9a but wasn't
updated in the grammar.
I've found that there are still huge amounts of occurrences of `task`s in the documentation. This PR tries to eliminate all of them in favor of `thread`.
This syntax was removed in b24a3b8 but references remained in the
grammar, the reference, rustdoc generation, and some auxiliary test
files that don't seem to have been used since 812637e.
An automated script was run against the `.rs` and `.md` files,
subsituting every occurrence of `task` with `thread`. In the `.rs`
files, only the texts in the comment blocks were affected.
Unicode escapes were changed in [this
RFC](28aeb3c391/text/0446-es6-unicode-escapes.md)
to use the ES6 \u{00FFFF} syntax with a variable number of digits from
1-6, eliminating the need for two different syntaxes for unicode
literals.
