Fix `@str` removal tests.
Changes from the review of the @str PR.
std,extra: remove use of & support for @[].
arena: stop using @[].
Update/delete tests using @[].
syntax: convert LitBinary from @[u8] to Rc<~[u8]>.
rustc: remove use of @[].
syntax: add an obsolete syntax warning for @[].
syntax: remove the handling of @str and @[] from the parser completely.
rustc: Remove the vstore handling of @str and @[].
syntax: remove the unused Vstore enum.

Seems to have been replaced by ExprVstore.
rustc: update docs & propagate @[]/@str removal more.

Various functions can now be made specific to ~[], or just non-managed
vectors.