r19426: merge nearly all the differences between Samba3 tdb and Samba4

r19426: merge nearly all the differences between Samba3 tdb and Samba4
tdb. This includes:

 - the new tdb_lockall and tdb_lockall_read code, which will be needed
   for the ldb speedups

 - the tdb logging changes. This is an intermediate step to keep the
   differences between the two branches small. The plan is still to
   move to a tdb_init()/tdb_set_logging_function()/tdb_attach() style
   of open which will make things much cleaner.

 - the updated test suites and standalone tdb build code

 - use libreplace headers

There are still some small differences I haven't merged. I'll discuss
those on the list.