Included low level rocksdb_mergeoperator_create

[Astn]

First, thanks for the great project!

I've been using your NuGet packages on Linux, and they have been working wonderfully.

I've been using WriteBatch to do Read/Modify/Write and wanted to switch to using WriteBatch.Merge but from the documentation, it seems I need to be able to call rocksdb_mergeoperator_create, which does not appear to be included in the NuGet package.

Thoughts?

[pablofrommars]

Hi,

Have a look at the pull request #28, it worked well for me to enable merge operators.

Regards