[12476] Add support for client 1.12.3 (build 6141) to realmd

Note for backporting: part in game/SharedDefine.h might be required in tbc already, see cmangos/mangos-classic#24

Signed-off-by: Schmoozerd <schmoozerd@cmangos>
[12477] Fix a VC90 compile problem. Also add some const correctness
[12478] Add some safety to rare case of target-selection for unreachable target

Thanks to Atari for reporting and researching this problem
[12479] Enable using table creature_linking with empty table creature_linking_template

Note: Guids are evil!
Close cmangos/issues#148
[12480] Improve unsummoning of wild-summoned GOs

This will fix some problems ie in Sunwell, thanks Atari for pointing

Signed-off-by: Schmoozerd <schmoozerd@cmangos.net>
[mr2810] fix Revitalize proc. close #1358
SD2 update