last fixes to make the testsuite work under mingw

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13636 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
Makefile.nt: make clean in the testsuite also

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13637 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
config/Makefile.mingw: bug in definition of ASPP

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13638 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02