Add sync_file_range to <fcntl.h>.

Bug: http://b/27952303
Change-Id: Idadfacd657ed415abc11684b9471e4e24c2fbf05
diff --git a/libc/libc.map.txt b/libc/libc.map.txt
index 9f2002f..d293264 100644
--- a/libc/libc.map.txt
+++ b/libc/libc.map.txt
@@ -1309,6 +1309,7 @@
     sigpause;
     sigrelse;
     sigset;
+    sync_file_range;
 } LIBC_N;
 
 LIBC_PRIVATE {