Don't mark __res_params or android_net_context as packed.

Bug: http://b/31532493

These internal API structures are never actually used anywhere that
would change behavior because it is "packed", so it is safe to remove.

Test: Builds correctly with the latest toolchain.
Change-Id: I5431992d840777605be75ab91dc21158d6d22c26
diff --git a/libc/dns/include/resolv_netid.h b/libc/dns/include/resolv_netid.h
index 7182ca6..37c1891 100644
--- a/libc/dns/include/resolv_netid.h
+++ b/libc/dns/include/resolv_netid.h
@@ -71,7 +71,7 @@
     unsigned dns_netid;
     unsigned dns_mark;
     uid_t uid;
-} __attribute__((packed));
+};
 
 #define NET_CONTEXT_INVALID_UID ((uid_t)-1)