Add griefing option to mcl_explosions.explode

When set to false explosions will only affect entities and not destroy
nodes.

mods/CORE/mcl_explosions/init.lua

@@ -141,6 +141,7 @@ end
 -- Values in info:
 -- drop_chance - The chance that destroyed nodes will drop their items
 -- fire - If true, 1/3 nodes become fire
+-- griefing - If true, the explosion will destroy nodes (default: true)
 --
 -- Note that this function has been optimized, it contains code which has been
 -- inlined to avoid function calls and unnecessary table creation. This was
@@ -171,6 +172,7 @@ local function trace_explode(pos, strength, raydirs, radius, info, puncher)
 	local fire = info.fire
 
 	-- Trace rays for environment destruction
+	if info.griefing then
 		for i = 1, #raydirs do
 			local rpos_x = pos.x
 			local rpos_y = pos.y
@@ -206,6 +208,7 @@ local function trace_explode(pos, strength, raydirs, radius, info, puncher)
 				end
 			end
 		end
+	end
 
 	-- Entities in radius of explosion
 	local punch_radius = 2 * strength
@@ -399,6 +402,7 @@ end
 -- sound - If true, the explosion will play a sound (default: true)
 -- particles - If true, the explosion will create particles (default: true)
 -- fire - If true, 1/3 nodes become fire (default: false)
+-- griefing - If true, the explosion will destroy nodes (default: true)
 function mcl_explosions.explode(pos, strength, info, puncher)
 	if info == nil then
 		info = {}
@@ -417,6 +421,7 @@ function mcl_explosions.explode(pos, strength, info, puncher)
 	if info.particles == nil then info.particles = true end
 	if info.sound == nil then info.sound = true end
 	if info.fire == nil then info.fire = false end
+	if info.griefing == nil then info.griefing = true end
 
 	-- For backwards compatability
 	if info.no_particle then info.particles = false end