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

ref/lua-5.1/test/env.lua

@@ -0,0 +1,7 @@
+-- read environment variables as if they were global variables
+
+local f=function (t,i) return os.getenv(i) end
+setmetatable(getfenv(),{__index=f})
+
+-- an example
+print(a,USER,PATH)