tweak tests/backtrace to also test ocamlopt
tweak tests/backtrace to also test ocamlopt

Note that native and byte-test share the same reference file, so in
particular they check that ocamlc and ocamlopt report uncaught
exception in the exact same way. Passing this test required a change
in asmrun/backtrace.c/print_location.


git-svn-id: e7e61699ce1738538ffebb75374fbea0924bc775@13810 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02

msprotz/ocaml,gerdstolpmann/ocaml,chambart/camlp4,msprotz/ocaml,eliberis/ocaml,msprotz/ocaml,yunxing/ocaml,eliberis/ocaml,eliberis/ocaml,hhugo/camlp4,eliberis/ocaml,msprotz/ocaml,yunxing/ocaml,yunxing/ocaml,yallop/camlp4,eliberis/ocaml,gerdstolpmann/ocaml,yunxing/ocaml,yunxing/ocaml,msprotz/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml