Add Lua 5.1 source files and documentation, including core libraries, interpreter, and test scripts.

ref/lua-5.1/test/readonly.lua

@@ -0,0 +1,12 @@
+-- make global variables readonly
+
+local f=function (t,i) error("cannot redefine global variable `"..i.."'",2) end
+local g={}
+local G=getfenv()
+setmetatable(g,{__index=G,__newindex=f})
+setfenv(1,g)
+
+-- an example
+rawset(g,"x",3)
+x=2
+y=1	-- cannot redefine `y'