The warning about malformed client-id is separated by a single
space character from the actual label. Also, used stream object
to concatenate label with suffix to be consistent with the
convention used in makeLabel.

    Added mention of hosts db to message text for DHCPSRV_MYSQL_HOST_DB_GET_VERSION

src/lib/dhcpsrv/host_data_source_factory.cc
    HostDataSourceFactory::create(const std::string& dbaccess)
        - Removed logging from exception throwing conditions
        - Minor clean up of the method itself

src/lib/dhcpsrv/dhcpsrv_messages.mes
    Removed obsoleted error messages:
        DHCPSRV_HOSTDB_NOTYPE
        DHCPSRV_UNKNOWN_HOST_DB

This reverts commit 8f2a1f8a, reversing
changes made to ed7edadc.

This  merge introduced regressions in our build farm and revealed
issues in the DHCP4o6 IPC code. It also revealed some differences
in sockets handling under Linux and BSD. Rather than continue
patching this here, we should work on the branch to resolve all
issues and then merge 1.1.

Added missing fctnl.h include. Okayed on jabber.

Removed debug leftover and changed 'responds' to 'answers'.

src/lib/dhcpsrv/dhcpsrv_messages.mes
    Added hosts database specific messages

src/lib/dhcpsrv/host_data_source_factory.cc
src/lib/dhcpsrv/mysql_host_data_source.cc
    Updated log statements with hosts database messages

src/bin/dhcp4/tests/dhcp4_srv_unittest.cc
    TEST_F(Dhcpv4SrvTest, emptyClientId)
        Added code to set up test interfaces

 - Includes fix in AllocEngine6Test ctor, provided by Thomas

This is a workaround for a GCC bug which affects gcc 4.4 and
manifests on RHEL6.3 as a build failure. This fix was okayed
on jabber.

Two nits.

This prevents compilation failure on OS-X. Reviewed and approved
on jabber.