Add dispell effect to ANTI_MAGIC

* fixes 0002156

lib/spells/BattleSpellMechanics.cpp

@@ -14,6 +14,31 @@
 #include "../NetPacks.h"
 #include "../BattleState.h"
 
+///AntimagicMechanics
+void AntimagicMechanics::applyBattle(BattleInfo * battle, const BattleSpellCast * packet) const
+{
+	DefaultSpellMechanics::applyBattle(battle, packet);
+
+	for(auto stackID : packet->affectedCres)
+	{
+		if(vstd::contains(packet->resisted, stackID))
+		{
+			logGlobal->errorStream() << "Resistance to positive spell " << owner->name;
+			continue;
+		}
+
+		CStack * s = battle->getStack(stackID);
+		s->popBonuses([&](const Bonus *b) -> bool
+		{
+			if(b->source == Bonus::SPELL_EFFECT)
+			{				
+				return b->sid != owner->id; //effect from this spell
+			}
+			return false; //not a spell effect
+		});
+	}	
+}
+
 ///ChainLightningMechanics
 std::set<const CStack *> ChainLightningMechanics::getAffectedStacks(SpellTargetingContext & ctx) const
 {

lib/spells/BattleSpellMechanics.h

@@ -12,6 +12,14 @@
 
 #include "CDefaultSpellMechanics.h"
 
+class DLL_LINKAGE AntimagicMechanics : public DefaultSpellMechanics
+{
+public:
+	AntimagicMechanics(CSpell * s): DefaultSpellMechanics(s){};	
+	
+	void applyBattle(BattleInfo * battle, const BattleSpellCast * packet) const override final;	
+};
+
 class DLL_LINKAGE ChainLightningMechanics : public DefaultSpellMechanics
 {
 public:

lib/spells/ISpellMechanics.cpp

@@ -28,6 +28,8 @@ ISpellMechanics * ISpellMechanics::createMechanics(CSpell * s)
 {
 	switch (s->id)
 	{
+	case SpellID::ANTI_MAGIC:
+		return new AntimagicMechanics(s);
 	case SpellID::ACID_BREATH_DAMAGE:
 		return new AcidBreathDamageMechanics(s);
 	case SpellID::CHAIN_LIGHTNING: