windows: don't define lseeki64 and lseek since they already exist.

Patch by Adrien Nader!

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13840 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
configure: use inf/wrn/err functions to write messages for the user.
(Patch by Adrien Nader!)

This makes messages to the user more consistent.

Behaviours:
  inf(): writes its arguments to stderr
  wrn(): writes "[WARNING]" to stderr and then its arguments to stderr
  err(): writes "[ERROR!]" to stderr, then its arguments to stderr, and
         calls "exit 2"

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13841 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
configure: fail if invoked with -param=value (instead of "-param value")

(Patch by Adrien Nader!)

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13842 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
configure: remove unused variables from case...in test.

(Patch by Adrien Nader!)

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13843 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
configure: fix detection of non-working C compiler.
(patch by Adrien Nader!)

The test tried to do something like:
  case "$foo,$bar" in
    *,*) echo 1 ;;
    *) echo "compiler not working" ;;
   esac
However the second case cannot match because of the first one.

Instead, check the return code of the command.

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13844 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
Fix PR#6056

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13845 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
test results

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13846 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02