Remove stable feature declarations

Closes #61

See merge request !66

Revert "Added 'oom' lang-item so downstream crates don't complain about missing 'oom' symbol"

See merge request !64

This reverts commit 7d7e3137

Make sure all tests and benches actually use ralloc as their global allocator

See merge request !63

Master

Closes #45

See merge request !62

Fixed occasional failing of 'partial_realloc'. This is because our bookkeeper's vec gets too cramped and should (theoretically) need resizing

Fix sbrk to actually return the *old* break.

 Use new allocator API, and otherwise update for new Rust

- New allocator API
- Remove the "allocator" feature, which should be unnecessary due to how
the new allocator API works
- NonZero no longer implements Deref (https://github.com/rust-lang/rust/pull/41064)
- NonZero::new() returns an Option; use NonZero::new_unchecked()
- Thread locals are no longer 'static (https://github.com/rust-lang/rust/pull/43746)
- Changes to feature flags
- Use unsafe to access extern static (https://github.com/rust-lang/rust/issues/36247)

MacOSX is not supported anymore

Grammar fix

it is missing some needed syscalls.

fixes #37

by switching from the syscall crate to the sc crate. The sc crate is a
fork of the syscall crate that adds supports for several other
platforms.

* fix the build

the `unborrow!` macro is need in the block and bookkeeper modules

* cfg(tls) away impl LocalAllocator

as the struct LocalAllocator is not available when the tls feature is
disabled

To avoid linking hell.

This feature is now in Rust stable, so adding !#[feature(question_mark)] is now useless and causes a warning.

We make the `Leak` trait unsafe and consituting an invariant. Secondly,
we implement `Leak` for all `Copy` types.

We equip all `unsafe` blocks with a timestamped confirmations of an
audit. Whenever a block is changed, it should be removed until a new
audit is made.

The format of these messages is:

```
LAST AUDIT: yyyy-mm-dd (Username)
```

Close #28.