Don't force location of tmp

(Logical change 1.14)
diff --git a/misc/ifstat.c b/misc/ifstat.c
index 67489b9..6e407d4 100644
--- a/misc/ifstat.c
+++ b/misc/ifstat.c
@@ -639,7 +639,7 @@
 	if (getenv("IFSTAT_HISTORY"))
 		snprintf(hist_name, sizeof(hist_name), getenv("IFSTAT_HISTORY"));
 	else
-		sprintf(hist_name, "/tmp/.ifstat.u%d", getuid());
+		sprintf(hist_name, "%s/.ifstat.u%d", P_tmpdir, getuid());
 
 	if (reset_history)
 		unlink(hist_name);