Conflicts:
	src/lib/datasrc/client_list.h

Also make the memory segment tests run only where shared memory is available.

Conflicts:
	src/lib/datasrc/memory/zone_table.cc
	src/lib/datasrc/memory/zone_writer.cc
	src/lib/datasrc/memory/zone_writer.h

Fixed Conflicts:
	ChangeLog

it now unconditionally uses AXFR, so mentioning possible failure of IXFR
doesn't make sense.

actually refresh wasn't defined in spec, so is defined now.
retransfer is revised so it always uses AXFR (BIND 9 compatible).
lettuce tests are adjusted accordingly.

it should now be safe as we (have already) support fallback and use AXFR
initially.

this is essentially a refactoring: there's no behavior change.
but it'll help later part of this branch.

also updated the test so the MockCC refers to the spec default, instead of
hardcoding the values.

no behavior change yet.  also, use AXFR by default, for now, to preserve
the behavior.

currently just recognize the option.  no behavior change due to it yet.

This change will be helpful for later part of this branch.

this class now doesn't rely on the low level interface anymore.

no behavior change.

 to bin/src/D2.