WIP: ldb: Remove independent version logic
Following on from !371 (closed) with the following changes:
- the tarball is still produced
- the version number of the tarball now matches the main Samba version number
Differing from what was written in https://lists.samba.org/archive/samba-technical/2019-April/133248.html
- The build system is unchanged, nothing is changed regarding integration into the main Samba build
The primary motivation here is to decouple ABI changes (eg adding a new function) from release points, and so slowing down to a 6-month release cycle matching the main release cadence of Samba so that new features have time to bake in master before they are released.
Samba versions are strictly locked to ldb release streams, so new ldb versions (from master) only cause trouble for distributors. If added to the archive they package maintainers have to do work to re-release the old version that the Samba package in the distribution can then use. This avoids this silly situation.
To be clear, an independent and smaller ldb tarball is still provided for distributors that desire it and to demonstrate that the build system remains independent of the main build.
The autobuild distcheck is also unchanged.
The MR to demonstrate the concept and to solicit feedback.