Export sprinttime

* defs.h (sprinttime): New prototype.
* file.c (sprinttime): Make global and move to util.c.
diff --git a/defs.h b/defs.h
index bcdf625..164842a 100644
--- a/defs.h
+++ b/defs.h
@@ -673,6 +673,7 @@
 extern int printflags(const struct xlat *, int, const char *);
 extern const char *sprintflags(const char *, const struct xlat *, int);
 extern const char *sprintmode(int);
+extern const char *sprinttime(time_t);
 extern void dumpiov_in_msghdr(struct tcb *, long);
 extern void dumpiov_in_mmsghdr(struct tcb *, long);
 extern void dumpiov(struct tcb *, int, long);