Fixed GIT_DELTA_CONFLICTED not returned in some cases

racy-git, the missing link

This is something we do on re-init but not when opening a
repository. This hasn't particularly mattered up to now as the version
has been 0 ever since the first release of git, but the times, they're
a-changing and we will soon see version 1 in the wild. We need to make
sure we don't open those.

git will assume the repository format version is 0 if the value is not
there. Do the same.

If an index entry for a file that is not in HEAD is in conflicted state,
when diffing HEAD with the index, the status field of the corresponding git_diff_delta was incorrectly reported as GIT_DELTA_ADDED instead of GIT_DELTA_CONFLICTED.

This was due to handle_unmatched_new_item() initially setting the status
to GIT_DELTA_CONFLICTED but then overriding it later with GIT_DELTA_ADDED.

This fixes a bug where if a file was in conflicted state in either diff,
it would not always remain in conflicted state in the merged diff.

Perform LF->CRLF for core.autocrlf=true on non-Win32 because core
git does.

Allow files to have mixed line endings instead of skipping processing
on them.

Use statistics (like core git) to control the behavior of the
to workdir CRLF filter.