Made a proper queued thread to client for handling some block mesh updates. Also made client mutex-free to allow easier adding of new stuff.

Modified block mesh generation to have clearer input and output. Instead of being a messy object oriented cludge, it now is a messy cludge with separate parameters.

fixed a possible infinite loop in ClientEnvironment (dtime counter getting so small that it doesn't increment the value)

--HG--
rename : data/luaobjects/test/client.lua => data/scripts/objects/test/client.lua
rename : data/luaobjects/test/server.lua => data/scripts/objects/test/server.lua

Fixed insufficient error handling in narrow_to_wide, which caused a crash if the path of the userdata directory contained special characters that were not included in the used charset (which is used because of the font)