A quick updated due a bug found by Hans while testing

mplib with wrong input.
The difference is only in rev: current is

This is LuaTeX, Version beta-0.79.3 (TeX Live 2015/dev) (rev 5140)

while previously was

This is LuaTeX, Version beta-0.79.3 (TeX Live 2015/dev) (rev 5130)

(in the future we will try to avoid a <minor>.<minor> number ).

luigi