Add new info functions to resolver for use by Netd.

android_net_res_stats_get_info_for_net returns the current name servers, search
domains, parameters and stats for the given network ID.

android_net_res_stats_aggregate provides statistics such as errors counts from
the raw stats data reported by android_net_res_stats_get_info_for_net.

android_net_res_stats_get_usable_servers uses the data returned by
android_net_res_stats_aggregate to determine which of the servers are
considered valid or broken by the resolver.

BUG: 25731675

Change-Id: I6059b68e5e8b809027a4d3135f6081588bee8a7d
diff --git a/libc/libc.map.txt b/libc/libc.map.txt
index f51c5d3..c7f9058 100644
--- a/libc/libc.map.txt
+++ b/libc/libc.map.txt
@@ -1533,3 +1533,10 @@
     wait3; # arm x86 mips nobrillo
     wcswcs; # arm x86 mips nobrillo
 } LIBC_O;
+
+LIBC_PLATFORM {
+  global:
+    android_net_res_stats_get_info_for_net;
+    android_net_res_stats_aggregate;
+    android_net_res_stats_get_usable_servers;
+} LIBC_O;