Crafting speedup

This greatly increases crafting performance, especially in worlds with many mods.

Approved by @kwolekr.

Introduces a hash-type-layered fall-through mechanism, where every layer specifies one hash algorithm,
and the "deeper the fall", the more collisions to expect for the algorithm. One Craft definition
only resides at one layer, which improves speed for lower layers (and a complete fail), due to most
craft definitions residing at high layers.

Due to the fall-through design, the undocumented behaviour that later craft recipes
override older ones had to be weaked up a bit, but craft recipes with the same hash and layer
will still override.

src/server.cpp

@@ -334,6 +334,9 @@ Server::Server(
 	// Perform pending node name resolutions
 	m_nodedef->runNodeResolverCallbacks();
 
+	// init the recipe hashes to speed up crafting
+	m_craftdef->initHashes(this);
+
 	// Initialize Environment
 	m_env = new ServerEnvironment(servermap, m_script, this, m_path_world);