sys.socket: make some more preprocessor constants conditional.
sys.socket: make some more preprocessor constants conditional.

* ext/posix/sys/socket.c (AI_ALL, AI_V4MAPPED): Add preprocessor
guards, as these two are not defined on at least OpenBSD 5.6.

Signed-off-by: Gary V. Vaughan <f9023000f29773649f3850298becb9544b5fd6a9@gnu.org>

luaposix/luaposix,zevv/luaposix,zevv/luaposix,ardje/luaposix,jimmyharris/luaposix,rrthomas/luaposix,ardje/luaposix,snegovick/luaposix,snegovick/luaposix,rrthomas/luaposix,jimmyharris/luaposix