Implement funopen64.

Bug: http://b/24807045
Change-Id: I161920978161389be34b707cc6ce8e05f760d552
diff --git a/libc/libc.x86.map b/libc/libc.x86.map
index f3bda0b..6497bf8 100644
--- a/libc/libc.x86.map
+++ b/libc/libc.x86.map
@@ -1217,6 +1217,7 @@
     freeifaddrs;
     fseeko64;
     fsetpos64;
+    funopen64;
     getgrgid_r;
     getgrnam_r;
     getifaddrs;