Create a quick P_StartQuake without epicenter/radius support and clean up the grand total of 4 earthquake uses in the code

src/k_kart.c

@@ -3157,10 +3157,7 @@ void K_ExplodePlayer(player_t *player, mobj_t *source, mobj_t *inflictor) // A b
 	K_PlayPainSound(player->mo);
 
 	if (P_IsDisplayPlayer(player))
-	{
+		P_StartQuake(64<<FRACBITS, 5);
-		quake.intensity = 64*FRACUNIT;
-		quake.time = 5;
-	}
 
 	player->kartstuff[k_instashield] = 15;
 	K_DropItems(player);

src/lua_baselib.c

@@ -1518,8 +1518,7 @@ static int lib_pStartQuake(lua_State *L)
 	quake.radius = luaL_optinteger(L, 4, 512*FRACUNIT);
 
 	// These things are actually used in 2.1.
-	quake.intensity = q_intensity;
+	P_StartQuake(q_intensity, q_time);
-	quake.time = q_time;
 	return 0;
 }
 

src/p_inter.c

@@ -3192,10 +3192,7 @@ boolean P_DamageMobj(mobj_t *target, mobj_t *inflictor, mobj_t *source, INT32 da
 				K_KartPainEnergyFling(player);
 
 				if (P_IsDisplayPlayer(player))
-				{
+					P_StartQuake(32<<FRACBITS, 5);
-					quake.intensity = 32*FRACUNIT;
-					quake.time = 5;
-				}
 			}
 			else
 				K_SpinPlayer(player, source, 0, inflictor, false);

src/p_spec.c

@@ -8273,3 +8273,11 @@ static void P_SearchForDisableLinedefs(void)
 		}
 	}
 }
+
+// Rudimentary function to start a earthquake.
+// epicenter and radius are not yet used.
+void P_StartQuake(fixed_t intensity, tic_t time)
+{
+	quake.intensity = intensity;
+	quake.time = time;
+}

src/p_spec.h

@@ -19,6 +19,10 @@
 
 extern mobj_t *skyboxmo[2];
 
+// Something that should've been done long ago???
+// We won't be using epicenter or radius anytime soon so I don't think it's worth it yet.
+void P_StartQuake(fixed_t intensity, tic_t time);
+
 // GETSECSPECIAL (specialval, section)
 //
 // Pulls out the special # from a particular section.