compiled dirstate extension breaks hashcache

On gutsy i386 0.92dev, with the extensions compiled I observe that bzr status reads and hashes all files, even when the dirstate ought to be up to date with their hash/stat information. This happens even when I run repeatedly. This is of course much slower.

lifeless suggested removing the extensions and that did fix it: on the next run, no files were read.

So it seems that the dirstate parsing code may be unpacking the stat fingerprint incorrectly, causing it to always miss - or something similar.