Added generic StepSound TERRAIN property.

Added a generic step sound TERRAIN property, for defining foot-agnostic step sounds. Used by the built-in footstep system over the individual foot ones.

src/gamedata/p_terrain.cpp

@@ -83,7 +83,8 @@ enum ETerrainKeywords
 	TR_RIGHTSTEPSOUNDS,
 	TR_LIQUID,
 	TR_FRICTION,
-	TR_ALLOWPROTECTION
+	TR_ALLOWPROTECTION,
+	TR_STEPSOUNDS
 };
 
 enum EGenericType
@@ -187,6 +188,7 @@ static const char *TerrainKeywords[] =
 	"friction",
 	"allowprotection",
 	"damageonland",
+	"stepsounds",
 	NULL
 };
 
@@ -223,6 +225,7 @@ static FGenericParse TerrainParser[] =
 	{ GEN_Custom, {(size_t)ParseFriction} },
 	{ GEN_Bool,   {myoffsetof(FTerrainDef, AllowProtection)} },
 	{ GEN_Bool,   {myoffsetof(FTerrainDef, DamageOnLand)} },
+	{ GEN_Sound,  {myoffsetof(FTerrainDef, StepSound)} },
 };
 
 
@@ -747,3 +750,4 @@ DEFINE_FIELD(FTerrainDef, AllowProtection)
 DEFINE_FIELD(FTerrainDef, DamageOnLand)
 DEFINE_FIELD(FTerrainDef, Friction)
 DEFINE_FIELD(FTerrainDef, MoveFactor)
+DEFINE_FIELD(FTerrainDef, StepSound)

src/gamedata/p_terrain.h

@@ -118,6 +118,7 @@ struct FTerrainDef
 	bool DamageOnLand;
 	double Friction;
 	double MoveFactor;
+	FSoundID StepSound;
 };
 
 extern TArray<FSplashDef> Splashes;

wadsrc/static/zscript/actors/player/player.zs

@@ -1742,6 +1742,15 @@ class PlayerPawn : Actor
 
 			if (Delay <= 0) return;
 
+			//Generic foot-agnostic sound takes precedence.
+			if (Ground.StepSound && GetAge() % Delay == 0)
+			{
+				A_StartSound (Ground.StepSound,flags:CHANF_OVERLAP,volume:Ground.StepVolume);
+				bool Heavy = Mass >= 200 ? 0 : THW_SMALL; //Big player makes big splash.
+				HitWater (CurSector,(Pos.XY,CurSector.FloorPlane.ZatPoint(Pos.XY)),True,False,flags:Heavy|THW_NOVEL);
+				return;
+			}
+
 			//Apparently most people walk with their right foot first, so assume that here.
 			bool LeftStep; //Prevent the right step playing twice.
 			if (GetAge() % (Delay*2) == 0)

wadsrc/static/zscript/doombase.zs

@@ -613,6 +613,7 @@ struct TerrainDef native
 	native bool DamageOnLand;
 	native double Friction;
 	native double MoveFactor;
+	native Sound StepSound;
 };
 
 enum EPickStart