Ported check_const from oldvisit to <V:Visitor> trait API.
Ported check_loop from oldvisit to <V:Visit> trait API.
Port check_match from oldvisit to <V:Visitor> trait API.
Port const_eval from oldvisit to <V:Visitor> trait API.
Ported effect checker from oldvisit to <V:Visitor> trait API.
Port privacy.rs from oldvisit to <V:Visitor> trait.
port reachable.rs from oldvisit to <V:Visitor> trait.
port region.rs from oldvisit to <V:Visitor> trait API.
Fix select deschedule environment race for real this time, in light of task killing.
Cleanup: remove useless parameter
Test for issue #6338.
Pointers to bound variables are stored after all patterns are matched.

Pointers to bound variables shouldn't be stored before checking pattern,
otherwise piped patterns can conflict with each other (issue #6338).

Closes #6338.
Fix error message when trait method ends with wrong token

When parsing a trait function, the function must end with either `;` or
`{` (signifying a default implementation). The error message incorrectly
stated that it must be `;` or `}`.

Fixes #6610.
Better error message for unknown start of token

The span was fixed at some point to point to the correct character, but
the error message is still bad. Update it to emit the actual character
in question (potentially escaped).

Fixes #3747.
doc: correct spelling in documentation.
doc: convert remaining uses of core:: to std::.
Implement DeepClone for str types.
Implement Clone and DeepClone for time types.
Give XorShiftRng::new() a random seed

Fixes #8359.
Reserve 'yield' keyword

Rename task::yield() to task::deschedule().

Fixes #8494.