dnsmasq: add option broadcast to host sections

There are certain consumer devices which are outliers in protocol conformance.
An example is Samsung bluray players, which require broadcast DHCP responses
(on Ethernet only, strangely not on Wifi).

By specifying:

config host
	...
	option broadcast 1

this will enable the response to be sent as an Ethernet broadcast and not as
a unicast.

Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38365 3c298f89-4303-0410-b956-a3cf2f4a3e73