missiles: add BUGFIXes for MI_LArrow, MI_Arrow, MI_Lightctrl and MI_Weapexp

These bugs are related to time of access, where fields of e.g. a
player or monster struct is accessed upon missile impact (instead
of missile launch), and at this point, the monster may be dead, or
the player may have left the game, resulting in accessing garbage
data that may have been overwritten by other data (e.g. new monster
spawn or new player joining).

One way to resolve this issue is to store e.g. the damage in the
missile struct when lanuching the missing. This way, the missile
would have all information required to know its damage on imact
instead of having to rely on outside sources that may no longer
be present.

Source/missiles.cpp

@@ -3735,6 +3735,7 @@ void MI_LArrow(int i)
 		rst = missiledata[missile[i]._mitype].mResist;
 		if (missile[i]._mitype == MIS_LARROW) {
 			if (p != -1) {
+				// BUGFIX: damage of missile should be encoded in missile struct; player can be dead/have left the game before missile arrives.
 				mind = plr[p]._pILMinDam;
 				maxd = plr[p]._pILMaxDam;
 			} else {
@@ -3746,6 +3747,7 @@ void MI_LArrow(int i)
 		}
 		if (missile[i]._mitype == MIS_FARROW) {
 			if (p != -1) {
+				// BUGFIX: damage of missile should be encoded in missile struct; player can be dead/have left the game before missile arrives.
 				mind = plr[p]._pIFMinDam;
 				maxd = plr[p]._pIFMaxDam;
 			} else {
@@ -3764,9 +3766,11 @@ void MI_LArrow(int i)
 
 		if (p != -1) {
 			if (missile[i]._micaster == TARGET_MONSTERS) {
+				// BUGFIX: damage of missile should be encoded in missile struct; player can be dead/have left the game before missile arrives.
 				mind = plr[p]._pIMinDam;
 				maxd = plr[p]._pIMaxDam;
 			} else {
+				// BUGFIX: damage of missile should be encoded in missile struct; monster can be dead before missile arrives.
 				mind = monster[p].mMinDamage;
 				maxd = monster[p].mMaxDamage;
 			}
@@ -3818,9 +3822,11 @@ void MI_Arrow(int i)
 	p = missile[i]._misource;
 	if (p != -1) {
 		if (missile[i]._micaster == TARGET_MONSTERS) {
+			// BUGFIX: damage of missile should be encoded in missile struct; player can be dead/have left the game before missile arrives.
 			mind = plr[p]._pIMinDam;
 			maxd = plr[p]._pIMaxDam;
 		} else {
+			// BUGFIX: damage of missile should be encoded in missile struct; monster can be dead before missile arrives.
 			mind = monster[p].mMinDamage;
 			maxd = monster[p].mMaxDamage;
 		}
@@ -3852,9 +3858,11 @@ void MI_Firebolt(int i)
 			if (missile[i]._micaster == TARGET_MONSTERS) {
 				switch (missile[i]._mitype) {
 				case MIS_FIREBOLT:
+					// BUGFIX: damage of missile should be encoded in missile struct; player can be dead/have left the game before missile arrives.
 					d = random_(75, 10) + (plr[p]._pMagic >> 3) + missile[i]._mispllvl + 1;
 					break;
 				case MIS_FLARE:
+					// BUGFIX: damage of missile should be encoded in missile struct; player can be dead/have left the game before missile arrives.
 					d = 3 * missile[i]._mispllvl - (plr[p]._pMagic >> 3) + (plr[p]._pMagic >> 1);
 					break;
 				case MIS_BONESPIRIT:
@@ -3862,6 +3870,7 @@ void MI_Firebolt(int i)
 					break;
 				}
 			} else {
+				// BUGFIX: damage of missile should be encoded in missile struct; monster can be dead before missile arrives.
 				d = monster[p].mMinDamage + random_(77, monster[p].mMaxDamage - monster[p].mMinDamage + 1);
 			}
 		} else {
@@ -4659,8 +4668,10 @@ void MI_Lightctrl(int i)
 	p = missile[i]._misource;
 	if (p != -1) {
 		if (missile[i]._micaster == TARGET_MONSTERS) {
+			// BUGFIX: damage of missile should be encoded in missile struct; player can be dead/have left the game before missile arrives.
 			dam = (random_(79, 2) + random_(79, plr[p]._pLevel) + 2) << 6;
 		} else {
+			// BUGFIX: damage of missile should be encoded in missile struct; monster can be dead before missile arrives.
 			dam = 2 * (monster[p].mMinDamage + random_(80, monster[p].mMaxDamage - monster[p].mMinDamage + 1));
 		}
 	} else {
@@ -5128,10 +5139,12 @@ void MI_Weapexp(int i)
 	missile[i]._mirange--;
 	id = missile[i]._misource;
 	if (missile[i]._miVar2 == 1) {
+		// BUGFIX: damage of missile should be encoded in missile struct; player can be dead/have left the game before missile arrives.
 		mind = plr[id]._pIFMinDam;
 		maxd = plr[id]._pIFMaxDam;
 		missiledata[missile[i]._mitype].mResist = MISR_FIRE;
 	} else {
+		// BUGFIX: damage of missile should be encoded in missile struct; player can be dead/have left the game before missile arrives.
 		mind = plr[id]._pILMinDam;
 		maxd = plr[id]._pILMaxDam;
 		missiledata[missile[i]._mitype].mResist = MISR_LIGHTNING;