[12802] Fix use of SpellBonusWithCoeffs

In case of taken damage/heal calculation the information of the caster must be used

Special thanks to Vladimir for clarifying and helping out

See cmangos/mangos-classic#104

Signed-off-by: Schmoozerd <schmoozerd@cmangos.net>
[12803] Implement instance data call for OnCreatureDespawn

Close cmangos/issues#534