Duke3D: Add global gameflag "DUKE3D_GLOBAL_ADDITIVE_HITRADIUS"

If this flag is set, all radius damage sources will apply cumulative
damage instead of overriding the existing accumulated damage.

Equivalent to applying PROJECTILE_HITRADIUS_ADDITIVE to all explosions.

source/duke3d/src/actors.cpp

@@ -200,7 +200,8 @@ void A_RadiusDamageObject_Internal(int const spriteNum, int const otherSprite, i
                 ++dmgFuzz;
 
             int dmgTotal = dmgBase + (krand()%(dmgFuzz-dmgBase));
-            if (SpriteProjectile[spriteNum].workslike & PROJECTILE_HITRADIUS_ADDITIVE)
+            if ((globalflags & DUKE3D_GLOBAL_ADDITIVE_HITRADIUS)
+                    | (SpriteProjectile[spriteNum].workslike & PROJECTILE_HITRADIUS_ADDITIVE))
                 dmgActor.htextra += dmgTotal;
             else
                 dmgActor.htextra = dmgTotal;

source/duke3d/src/global.h

@@ -60,6 +60,7 @@ enum DUKE3D_GLOBALFLAGS {
     DUKE3D_NO_WIDESCREEN_PINNING = 1<<0,
     DUKE3D_NO_HARDCODED_FOGPALS = 1<<1,
     DUKE3D_NO_PALETTE_CHANGES = 1<<2,
+    DUKE3D_GLOBAL_ADDITIVE_HITRADIUS = 1<<3,
 };
 
 G_EXTERN DukeStatus_t sbar;