TNT: start fire nodetimers for created fire nodes.

Without this patch, any fire created(placed) by tnt explosions
will remain forever on the map.

mods/tnt/init.lua

@@ -83,7 +83,10 @@ local function add_drop(drops, item)
 	end
 end
 
-local function destroy(drops, npos, cid, c_air, c_fire, on_blast_queue, ignore_protection, ignore_on_blast)
+local basic_flame_on_construct -- cached value
+local function destroy(drops, npos, cid, c_air, c_fire,
+		on_blast_queue, on_construct_queue,
+		ignore_protection, ignore_on_blast)
 	if not ignore_protection and minetest.is_protected(npos, "") then
 		return cid
 	end
@@ -93,9 +96,16 @@ local function destroy(drops, npos, cid, c_air, c_fire, on_blast_queue, ignore_p
 	if not def then
 		return c_air
 	elseif not ignore_on_blast and def.on_blast then
-		on_blast_queue[#on_blast_queue + 1] = {pos = vector.new(npos), on_blast = def.on_blast}
+		on_blast_queue[#on_blast_queue + 1] = {
+			pos = vector.new(npos),
+			on_blast = def.on_blast
+		}
 		return cid
 	elseif def.flammable then
+		on_construct_queue[#on_construct_queue + 1] = {
+			fn = basic_flame_on_construct,
+			pos = vector.new(npos)
+		}
 		return c_fire
 	else
 		local node_drops = minetest.get_node_drops(def.name, "")
@@ -306,6 +316,8 @@ local function tnt_explode(pos, radius, ignore_protection, ignore_on_blast)
 
 	local drops = {}
 	local on_blast_queue = {}
+	local on_construct_queue = {}
+	basic_flame_on_construct = minetest.registered_nodes["fire:basic_flame"].on_construct
 
 	local c_fire = minetest.get_content_id("fire:basic_flame")
 	for z = -radius, radius do
@@ -318,8 +330,8 @@ local function tnt_explode(pos, radius, ignore_protection, ignore_on_blast)
 			local p = {x = pos.x + x, y = pos.y + y, z = pos.z + z}
 			if cid ~= c_air then
 				data[vi] = destroy(drops, p, cid, c_air, c_fire,
-					on_blast_queue, ignore_protection,
+					on_blast_queue, on_construct_queue,
-					ignore_on_blast)
+					ignore_protection, ignore_on_blast)
 			end
 		end
 		vi = vi + 1
@@ -357,6 +369,10 @@ local function tnt_explode(pos, radius, ignore_protection, ignore_on_blast)
 		end
 	end
 
+	for _, queued_data in pairs(on_construct_queue) do
+		queued_data.fn(queued_data.pos)
+	end
+
 	return drops, radius
 end