dirstate.status: assign members one by one instead of unpacking the tuple
With this patch, hg status and hg diff regain their previous speed.
The following tests are run against a working copy with over 270,000 files.
Here, 'before' means without this or the previous patch applied.
Note that in this case `hg perfstatus` isn't representative since it doesn't
take dirstate parsing time into account.
$ time hg status # best of 5
before: 2.03s user 1.25s system 99% cpu 3.290 total
after: 2.01s user 1.25s system 99% cpu 3.261 total
$ time hg diff # best of 5
before: 1.32s user 0.78s system 99% cpu 2.105 total
after: 1.27s user 0.79s system 99% cpu 2.066 total