Core/Spells: drop last leftovers of hardcoded spell target selection and move it into spellscripts

Closes #1719
Closes #3186
Core/Misc: Missing changes and get rid of useless method in acd46085d1f496657e27e0d5f823f53d466702dc
Core/Splines: Fix "velocity > 0.1f" error

Updates #6191.
Scripts/HoR: Fix log error

Fix "DoZoneInCombat called for creature that has empty threat list" error caused by DoZoneInCombat() called by IsSummonedBy() in a script before the Creature is allowed to enter combat.
Fix warnings introduced on littleendian in 2134cb610d45727a0623741f7416a360882133fa

This fix prevents possible issues on bigendian machines. Don't use c style casts ppl, it's evul.