Implement funopen64.

Bug: http://b/24807045
Change-Id: I161920978161389be34b707cc6ce8e05f760d552
diff --git a/libc/libc.map.txt b/libc/libc.map.txt
index 9317f81..32ef22a 100644
--- a/libc/libc.map.txt
+++ b/libc/libc.map.txt
@@ -1260,6 +1260,7 @@
     freeifaddrs;
     fseeko64;
     fsetpos64;
+    funopen64;
     getgrgid_r;
     getgrnam_r;
     getifaddrs;