rename `at_vec::from_owned` and `at_vec::from_slice` to `at_vec::to_managed_consume` and `at_vec::to_managed`
Add unsetenv wrapper
syntax: deprecate #[auto_{en,de}code] in favour of #[deriving({En,De}codable)].

Replace all instances of #[auto_*code] with the appropriate #[deriving] attribute
and remove the majority of the actual code, leaving stubs to refer the user to
the new syntax.
add DeepClone impl for @T and @mut T with T: Const
auto merge of #6502 : huonw/rust/no-auto-code, r=graydon

Replace all instances of #[auto_*code] with the appropriate #[deriving] attribute
and remove the majority of the actual auto_* code, leaving stubs to refer the user to
the new syntax.

Also, moves the useful contents of auto_encode.rs to more appropriate spots: tests and comments to deriving/encodable.rs, and the ExtCtxtMethods trait to build.rs (unused so far, but the method syntax might be nicer than using the mk_* fns in many instances).
auto merge of #6503 : sonwow/rust/at_vec-renamed, r=graydon

`str::from_slice` and `vec::from_slice` are changed to `str::to_owned` and `vec::to_owned`. (#6389)

Replace `at_vec::from_owned` and `at_vec::from_slice` with `at_vec::to_managed_consume` and `at_vec::to_managed`.
auto merge of #6527 : thestinger/rust/deep_clone, r=pcwalton
auto merge of #6505 : cmr/rust/unsetenv, r=catamorphism
Change unsafe functions to safe functions
auto merge of #6488 : sammykim/rust/issue-6430, r=sanxiyn

Fix issue #6430.
core: Document some intrinsics