tizenrt: Skip IPv6 code if feature disabled (#118)
tizenrt: Skip IPv6 code if feature disabled (#118)

Observed issue while building IoT.js (master)
on TizenRT (master) with artik055s/nettest config:

    arm-none-eabi-ld (...) \
    -o ".../build/output/bin/tinyara" (...) \
    .../build/output/bin/tinyara.map \
    .../build/output/libraries/libtuv.a(udp.c.obj): \
    In function `uv__udp_maybe_deferred_bind': \
    TizenRT/external/iotjs/deps/libtuv/src/unix/udp.c:445: \
    undefined reference to `in6addr_any'

Note TizenRT's artik055s/nettest image hasn't CONFIG_NET_IPv6 defined,
while artik053 has it, both should be aligned.

Bug: https://github.com/Samsung/libtuv/pull/118
libtuv-DCO-1.0-Signed-off-by: Philippe Coval p.coval@samsung.com
Samsung/libtuv,Samsung/libtuv,Samsung/libtuv