Expose __res_randomid.

I don't think this will help the original submitter, because <resolv.h>
is mostly useless on Android. One day we might have a deprecation and
removal policy for the NDK, but until then we should probably maintain
this header.

Bug: https://github.com/android-ndk/ndk/issues/739
Test: ran tests
Change-Id: I2db859abfdebc3824c997462fa6133d5b355a8dd
diff --git a/libc/libc.arm.map b/libc/libc.arm.map
index 18099dd..a133804 100644
--- a/libc/libc.arm.map
+++ b/libc/libc.arm.map
@@ -1420,6 +1420,11 @@
     wcstoul_l;
 } LIBC_O;
 
+LIBC_Q { # introduced=Q
+  global:
+    __res_randomid;
+} LIBC_P;
+
 LIBC_PRIVATE {
   global:
     ___Unwind_Backtrace; # arm