Fix visibility for a bunch more symbols.

Bug: 11156955
Bug: 15291317

(cherry picked from commit a167eef5482d4a89d4277ec74f57adbe38052813)

Change-Id: Ib038ad34ef59631f7b4ed6dff2b7956001b8b159
diff --git a/libc/upstream-netbsd/android/include/namespace.h b/libc/upstream-netbsd/android/include/namespace.h
index a4d4151..5df543c 100644
--- a/libc/upstream-netbsd/android/include/namespace.h
+++ b/libc/upstream-netbsd/android/include/namespace.h
@@ -22,4 +22,7 @@
 #undef __weak_alias
 #endif
 
+__LIBC_HIDDEN__ int __res_enable_mt(void);
+__LIBC_HIDDEN__ int __res_disable_mt(void);
+
 #endif