dnsmasq: simplify build configuration

dnsmasq: simplify build configuration

Drop direct sed'ing of config.h for HAVE_CONNTRACK, HAVE_LUASCRIPT, and
HAVE_DBUS. Use MAKE_OPTS COPTS parameters instead, like we do already
for all other options.

Rename DNSMASQ_ENABLE_LUA to DNSMASQ_TWEAK_LIBLUA since it now does only
that.

Merge two conntrack and three dbus conditional sections.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
(cherry picked from commit 1042fea88aea4ebddcac5e215286394f1ad012b4)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>