`flexdll_dlopen` receives a `char *` argument (library filename) that gets passed to `LoadLibraryEx`/`LoadLibrary`. We need a version taking `wchar_t *` and calling `LoadLibraryExW`/`LoadLibraryW`. Related to ocaml/ocaml#1200.
flexdll_dlopenreceives achar *argument (library filename) that gets passed toLoadLibraryEx/LoadLibrary.We need a version taking
wchar_t *and callingLoadLibraryExW/LoadLibraryW.Related to ocaml/ocaml#1200.