Unused since " tdb: no longer need seqnum store hack as we can read after prepare."

Generally clean up temp file handling.

This means we should skip building if there are no C files in module: running tests requires building the module, but not necessarily that it has any C files.

(Imported from SAMBA commit 46c99ec2a3781d53138245182345c6c2ddd9a258:
From: Andrew Tridgell <tridge@samba.org>
Date: Tue, 15 Sep 2009 14:04:22 -0700

We previously only allowed a commit to happen after a prepare
commit. It is in fact safe to allow reads between a prepare and a
commit, and the s4 replication code can make use of that, so allow it.

More sophisticated skipping: skip dependencies when one fails as well.
Allow tests to change their total_score; only access it after running (other than to check it's non-zero).

This bug was introduced in "Wean off TDB_ERRCODE.".

Despite the name, they're simple byte locks, not whole-file.

Explicitly split lock and unlock, for future replacement with user-supplied functions.
Use explicit flags enum for marking, blocking and probing.
Indicate upon unlock whether we had a read or write lock (POSIX doesn't care, but
wrappers might, and it's nice to be explicit).

ie.  f1c6f7dd47bb1081781c0a0d567a92bbbc0aa5d5 (Revert "add TDB_NO_NESTING...")
and  3e49e41c21eb8c53084aa8cc7fd3557bdd8eb7b6 (New attempt at TDB transaction nesting allow/disallow).

In future, this may happen, and we don't want to clobber them.

It was a regrettable hack to reduce line count in tdb; in fact it caused confusion as can be seen in this patch.
In particular, ecode now needs to be set before TDB_LOG.
Also, we should never set errno, as io.c was doing.

commit a6cc04a20089e8fbcce138c271961c37ddcd6c34
Author: Andrew Tridgell <tridge@samba.org>
Date:   Mon Jun 1 13:13:07 2009 +1000

    overallocate all records by 25%
    
    This greatly reduces the fragmentation of databases where records
    tend to grow slowly by a small amount each time. The case where this
    is most seen is the ldb index records. Adding this overallocation
    reduced the size of the resulting database by more than 20x when
    running a test that adds 10k users.

commit a386173fa1c7c5bcc11ea9260d84b6c52c154b3d
Author: Andrew Tridgell <tridge@samba.org>
Date:   Mon Jun 1 13:11:39 2009 +1000

    auto-repack in transactions that expand the tdb
    
    The idea behind this is to recover from badly fragmented free
    lists. Choosing the point where the file expands is fairly arbitrary,
    but seems to work well.

commit 936d76802f98d04d9743b2ca8eeeaadd4362db51
Author: Andrew Tridgell <tridge@samba.org>
Date:   Tue Dec 16 14:38:17 2008 +1100

    imported the tdb_repack() code from CTDB
    
    The tdb_repack() function repacks a TDB so that it has a single
    freelist entry. The file doesn't shrink, but it does remove all
    freelist fragmentation. This code originated in the CTDB vacuuming
    code, but will now be used in ldb to cope with fragmentation from
    re-indexing