Makefile.nt: install .mli files to the compilerlibs directory
Makefile.nt: install .mli files to the compilerlibs directory

Before this commit, the mli files of the utils, parsing, typing, bytecomp,
driver and toplevel directories were not installed to the compilerlibs
directory on Windows as was done on Unix. This commit fixes this.

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