Added directory scanning example, and enabled posix routines in Lua for unix environment

examples/lua/dirscan.lp

@@ -0,0 +1,15 @@
+HTTP/1.0 200 OK
+Content-Type: text/plain
+
+<?
+  -- Directory scanning example
+
+  function scandir(dir)
+    local t = {}
+    for f in io.popen('dir ' .. dir):lines() do table.insert(t, f) end
+    return t
+  end
+
+  local tab = scandir('C:\\')
+  for k,v in pairs(tab) do mg.write(v, '\n') end
+?>