ChangeLog - added an entry

src/bin/dhcp4/tests/fqdn_unittest.cc
    TEST_F(NameDhcpv4SrvTest, serverUpdateMalformedHostname) - added
    commentary

src/lib/exceptions/isc_assert.h
    commentary changes

src/lib/exceptions/tests/exceptions_unittest.cc
    TEST(IscThrowAssert, checkMessage) - replace use of explicit line number