Add support for language variants/dialects.

Assuming the detected language is `ll_CC`, the
mod tries the following files:

- `locale/ll_CC.txt`
- `locale/ll.txt`
- `locale/en.txt` (assuming it has not been
  processed already).

init.lua

@@ -16,7 +16,6 @@ dofile(MP.."/lib.lua")
 local LANG = minetest.setting_get("language")
 if not (LANG and (LANG ~= "")) then LANG = os.getenv("LANG") end
 if not (LANG and (LANG ~= "")) then LANG = "en" end
-LANG = LANG:sub(1, 2)
 
 
 local INS_CHAR = intllib.INSERTION_CHAR
@@ -61,14 +60,31 @@ function intllib.Getter(modname)
 end
 
 
-function intllib.get_strings(modname)
+local function get_locales(code)
+	local ll, cc = code:match("^(..)_(..)")
+	if ll then
+		return { ll.."_"..cc, ll, ll~="en" and "en" or nil }
+	else
+		return { code, code~="en" and "en" or nil }
+	end
+end
+
+
+function intllib.get_strings(modname, langcode)
+	langcode = langcode or LANG
 	modname = modname or minetest.get_current_modname()
 	local msgstr = intllib.strings[modname]
 	if not msgstr then
 		local modpath = minetest.get_modpath(modname)
-		msgstr = intllib.load_strings(modpath.."/locale/"..LANG..".txt")
+		msgstr = { }
+		for _, l in ipairs(get_locales(langcode)) do
+			local t = intllib.load_strings(modpath.."/locale/"..l..".txt") or { }
+			for k, v in pairs(t) do
+				msgstr[k] = msgstr[k] or v
+			end
+		end
 		intllib.strings[modname] = msgstr
 	end
-	return msgstr or nil
+	return msgstr
 end