Replace chained concatenation reassignment with simple concatenation

Example:

x = y
x = x .. z

Fixed:

x = y
.. z

This simple fix would save 1 string creation/deletion. Most changes
involve many more than this.

nselib/wsdd.lua

@@ -165,9 +165,9 @@ Decoders = {
   -- @return status true on success, false on failure
   -- @return err string containing the error message
   ['error'] = function( data )
-    local response = "Failed to decode response from device: "
     local err = data:match("<SOAP.-ENV:Reason><SOAP.-ENV:Text>(.-)<")
-    response = response .. (err or "Unknown error")
+    local response = "Failed to decode response from device: "
+    .. (err or "Unknown error")
 
     return true, response
   end,