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_params.h b/libc/dns/include/resolv_params.h
index 5ee265f..49ae691 100644
--- a/libc/dns/include/resolv_params.h
+++ b/libc/dns/include/resolv_params.h
@@ -41,6 +41,6 @@
     uint8_t success_threshold; // 0: disable, value / 100 otherwise
     uint8_t min_samples; // min # samples needed for statistics to be considered meaningful
     uint8_t max_samples; // max # samples taken into account for statistics
-} __attribute__((__packed__));
+};
 
 #endif // _RESOLV_PARAMS_H