Cleanup client init states by bumping protocol version

Don't use TOSERVER_RECEIVED_MEDIA but TOSERVER_CLIENT_READY as indicatio for client ready
Handle clients with protocol version < 23 (almost) same way as before
Make client tell server about it's version
Add client state to not send bogus player position updates prior init complete
Add access to statistics information (peer connction time,rtt,version)
Fix clients standing stalled in world while preloading item visuals (new clients only)
Add get_player_information to read client specific information from lua

doc/lua_api.txt

@@ -1200,6 +1200,29 @@ minetest.features
 minetest.has_feature(arg) -> bool, missing_features
 ^ arg: string or table in format {foo=true, bar=true}
 ^ missing_features: {foo=true, bar=true}
+minetest.get_player_information(playername)
+^ table containing information about player peer:
+{
+	address = "127.0.0.1",     -- ip address of client
+	ip_version = 4,            -- IPv4 / IPv6
+	min_rtt = 0.01,            -- minimum round trip time
+	max_rtt = 0.2,             -- maximum round trip time
+	avg_rtt = 0.02,            -- average round trip time
+	min_jitter = 0.01,         -- minimum packet time jitter
+	max_jitter = 0.5,          -- maximum packet time jitter
+	avg_jitter = 0.03,         -- average packet time jitter
+	connection_uptime = 200,   -- seconds since client connected
+	
+	-- following information is available on debug build only!!!
+	-- DO NOT USE IN MODS
+	--ser_vers = 26,             -- serialization version used by client
+	--prot_vers = 23,            -- protocol version used by client
+	--major = 0,                 -- major version number
+	--minor = 4,                 -- minor version number
+	--patch = 10,                -- patch version number
+	--vers_string = "0.4.9-git", -- full version string
+	--state = "Active"           -- current client state
+}
 
 Logging:
 minetest.debug(line)