This is a simple database API. It was inspired by the realisation that
in Samba we have several ad-hoc bits of code that essentially
implement small databases for sharing structures between parts of
Samba. As I was about to add another I realised that a generic
database module was called for to replace all the ad-hoc bits.

I based the interface on gdbm. I couldn't use gdbm as we need to be
able to have multiple writers to the databases at one time.

Compilation
-----------

add HAVE_MMAP=1 to use mmap instead of read/write
add TDB_DEBUG for verbose debug info
add NOLOCK=1 to disable locking code

Testing
-------

Compile tdbtest.c and link with gdbm for testing. tdbtest will perform
identical operations via tdb and gdbm then make sure the result is the
same

Interface
---------

The interface is very similar to gdbm except for the following:

- different open interface. The tdb_open call is more similar to a
  traditional open()
- no tdbm_reorganise() function
- no tdbm_sync() function. No operations are cached in the library anyway
- added a tdb_traverse() function for traversing the whole database