Think about reintroducing the `MDB_IDL_LOGN` features

[Clément Renault]

The Mozilla team changed the midl.h file and made the MDB_IDL_LOGN define customizable using a Cargo TOML feature. This change was made to reduce the number of free pages when opening a database in read-write mode.

A bunch of questions for this issue to be closed:

1. Do we care about this parameter for Meilisearch?
2. Do other companies need this?
3. Should we reintroduce this patch to the LMDB source code?
4. Should hyc introduce the #ifndef #endif changes in the official source code?

[Clément Renault]

Implemented by #229.