ldb_operr() instead of LDB_ERR_OPERATIONS_ERROR

[tridge at samba.org]

Hi Matthieu,

As we discussed on IRC, I've been making some patches for ldb to
reduce the number of instances where we return
LDB_ERR_OPERATIONS_ERROR without any explanatory error string. The
idea is to make it easier to track down problems like you have been
seeing in the provision code.

I've now pushed that to a ldb-error branch in my git tree. Can you
please try it out?

Simo, could you also please take a look.

Ideally we would set a meaningful error string on every error
instance, but that it not feasible in the time I have available for
this, so the patch instead uses file:line based error strings in cases
where we did not already set an error.

It also changes ldb_oom() to return an error code, so we can now do:

 return ldb_oom(ldb);

instead of:

 ldb_oom(ldb);
 return LDB_ERR_OPERATIONS_ERROR;

Patches are here:

  http://git.samba.org/?p=tridge/samba.git;a=log;h=refs/heads/ldb-error

Cheers, Tridge