An LMDB bump and some unsafe methods
In this PR we are:
- breaking the library by really specifying what is unsafe, the
del_current
,put_current
, andappend
iterator methods are unsafe now and it because you must know what you are doing when you use them: you must not retain any reference from inside the database when calling them. You can read more on the pull request. - bumping LMDb to the latest version (v0.9.70) by using a fork of Mozilla's repository. However, we will not be able to publish this in crates.io for now.