Expose ftello64.

Also add the missing test that would have caught this.

Bug: http://b/24807045
Change-Id: I756a4d825595b52396b15898e3f717156fd1ba2f
diff --git a/libc/libc.arm.map b/libc/libc.arm.map
index 02dd58c..001476e 100644
--- a/libc/libc.arm.map
+++ b/libc/libc.arm.map
@@ -1229,6 +1229,7 @@
     freeifaddrs;
     fseeko64;
     fsetpos64;
+    ftello64;
     funopen64;
     getgrgid_r;
     getgrnam_r;