Add job with system compiler

 + Rename jobs too.

.gitlab-ci.yml

@@ -2,6 +2,10 @@ before_script:
   - apt-get update -qq && apt-get install -y -qq opam
   - opam --version
 
+# OCaml version of the ci runner, i.e. from the system
+ocaml_sys:
+  script: "opam init;./configure --enable-tests;make test;opam pin add oclaunch ."
+
 # OCaml version 4.02
-ocaml402:
+ocaml_402:
   script: "opam init --comp 4.02.3;./configure --enable-tests;make test;opam pin add oclaunch ."