submodule: normalize slashes in resolve_url
submodule: normalize slashes in resolve_url

Our path functions expect to work with slashes, so convert a
path with backslashes into one with slashes at the top of
the function.

nokiddin/libgit2,nokiddin/libgit2,nokiddin/libgit2,nokiddin/libgit2,nokiddin/libgit2,nokiddin/libgit2