For some reason, on Solaris this causes types "uintXX_t" to become
undefined.  The "using" statement was removed and an explicit
namespace prepended to declarations of shared_ptr and dynamic_pointer_cast.

The allocation engine is now pointed to by a shared pointer.  Previously
it was pointed toi by a raw pointer and not deleted in the destructor.
Also, use an automatic variable to hold the DHCP6 server in the
unit tests.

From http://bind10.isc.org/ticket/2468#comment:2 to help troubleshoot later.

Okayed via jabber.

this is necessary for Solaris. okayed on jabber.

DNS_SERVERS option is now sent only if requested by clients
 (as it should be)

Conflicts:
	src/bin/dhcp6/dhcp6_messages.mes
	src/bin/dhcp6/dhcp6_srv.cc
	src/bin/dhcp6/dhcp6_srv.h
	src/bin/dhcp6/tests/dhcp6_srv_unittest.cc
	src/lib/dhcp/addr_utilities.cc
	src/lib/dhcp/tests/cfgmgr_unittest.cc

Files automerged successfully:
    src/lib/dhcp/alloc_engine.cc
    src/lib/dhcp/subnet.h
    src/lib/dhcp/tests/alloc_engine_unittest.cc

 commit.

do this only when stdin is a terminal; otherwise some lettuce tests will fail,
and it would possibly break some other automatic processing scripts.

based on review discussions.  it makes sense as we cannot assume its address
is never needed in non test applications.

This fixes build issues discovered during code review.