Add futimes, futimesat, and lutimes.

Spotted these while cleaning up <sys/cdefs.h> --- if we remove __USE_XOPEN2K8,
libchrome decides you "must" have futimes. Adding the missing functions (all
just alternative interfaces to utimensat(2) system call) lets us clean up
without breaking anything.

Change-Id: If44fab08ee3de0e31066d650d128a3c96323529b
diff --git a/libc/libc.arm.map b/libc/libc.arm.map
index a1b2511..f6520b5 100644
--- a/libc/libc.arm.map
+++ b/libc/libc.arm.map
@@ -1273,11 +1273,14 @@
     catopen;
     endgrent;
     endpwent;
+    futimes;
+    futimesat;
     getdomainname;
     getgrent;
     getpwent;
     getsubopt;
     hasmntopt;
+    lutimes;
     mblen;
     pthread_getname_np;
     quotactl;