Custom allocator support

[Colecf]

Would it be possible to support custom allocators in dashmap? I'd like to try using it with bumpalo.

I know that hashbrown supports it.

[lylythechosenone]

Currently, allocator_api (the feature you are referring to) is unstable. Using it would require nightly. Although, this could be done with the allocator_api2 crate for now.

[anthony-crystalpeak]

could we gate this behind a nightly feature the same as hashbrown? Lack of this feature might force me to revert to RwLock<HashMap> :<

[MathGeniusJodie]

I would also really want this, it would allow having the map in a mmapped file

[anthony-crystalpeak]

With some support for cross-process futex/locks, it could also be placed in shared memory across processes which was my use case.