[z2080] Add wrapper to access spell locations

* Add SpellCastTargets::getSource to get the source position (for TARGET_FLAG_SOURCE_LOCATION)
* Add SpellCastTargets::getDestination to get the destination position (for TARGET_FLAG_DEST_LOCATION)

(based on commit [12119] - bd83456)

Signed-off-by: stfx <stfx@hotmail.de>

(based on commit [s1698] - 7eed427)