Update todo backports from master branch

An updated and shorter version of backport that _may_ be backported from master branch.

I removed every commit that should not be backported (already backported, already in TBC todo list, not a 1.12 feature, hack...)

I left the commits I made and that I'm sure should be backported.

Most of the other commits should be discussed before backporting :
- related to codestyle
- changes not documented
- changes that I don't understand the purpose
- changes that I'm not sure that they are accurate (research needed)
- changes related to maps/vmaps now that mmaps are in cmangos-classic

Please, feel free to ask me if more work on this list is required. :)