arcshift 0.4.4

Replacement for std::sync::Arc<T> that supports updating the value, with some caveats.
Documentation
## 0.4.4
Fix error in test suite, formatting test wasn't run correctly in loom.

## 0.4.3

Fix Debug impl of ArcShift, so that it honors "{:#?}" format strings.

## 0.4.2

Support rust 1.75 (0.4.1 regressed to require newer rust).

## 0.4.1

Support 32-bit platforms. Prior to this version, ArcShift did not provide correct information
to the allocator when deallocating heap blocks on 32-bit platforms.

## 0.4.0

`ArcShift<T>` now implements `Default` if `T:Default`.