[PATCH 0 of 3] largefiles: fix issues with inappropriate locking and lfdirstate status

[Na'Tosha Bard]

This patch series fixes issues with incorrect dirstate status (as seen by
precommit hooks) and inappropriate locking.  Largefiles previously violated
Mercurial's locking model (as seen in issue 3182).  In the process of fixing
this, it became apaprent that the dirstate status was not reliable when
called from a precommit hook.  This patch series fixes these issues, and
updates the largefiles test to run a precommit hook that can detect
both inappropriate locking and the validity of status when called from a
precommit hook.

If necessary, changeset f3dd3c4abd56 can stand by itself as a separately
applied patch.