Add support for the utimensat(2) syscall to bionic.

The kernel has supported this syscall for quite some time now,
but bionic did not.  Now that there is a need for it, let's
add it to bionic.

Change-Id: Ifcef3e46f1438d79435b600c4e6063857ab16903
diff --git a/libc/SYSCALLS.TXT b/libc/SYSCALLS.TXT
index bd3e4d4..d698133 100644
--- a/libc/SYSCALLS.TXT
+++ b/libc/SYSCALLS.TXT
@@ -174,6 +174,7 @@
 int           __timer_getoverrun:timer_getoverrun(timer_t)                                              260,262
 int           __timer_delete:timer_delete(timer_t)                                                      261,263
 int           utimes(const char*, const struct timeval tvp[2])                          269, 271
+int           utimensat(int, const char *, const struct timespec times[2], int)         348, 320, 320
 
 # signals
 int     sigaction(int, const struct sigaction *, struct sigaction *)  67