Merge pull request #1333 from camlunity/master

+ extlib 1.6.0
Declare that js_of_ocaml 1.3.1 is not compatible with compiler version 4.01.0
Merge pull request #1334 from pveber/patch-2

Declare that js_of_ocaml 1.3.1 is not compatible with compiler version 4.01.0
msgpack: fix uninstall