In caml_executable_name(), wrong test on the return code of readlink()
In caml_executable_name(), wrong test on the return code of readlink()

Follow-up to PR#795 "More robust determination of full path to current executable"

gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml