Add memory usage to dstat output

Adds used, buffers, cache, free values next to the CPU usage.

Change-Id: Ia873e6a5e78413b724464985b253149bc7e9e2d8
diff --git a/stack.sh b/stack.sh
index a4e6bfd..91f188f 100755
--- a/stack.sh
+++ b/stack.sh
@@ -884,7 +884,7 @@
 # -------
 
 # A better kind of sysstat, with the top process per time slice
-DSTAT_OPTS="-tcndrylp --top-cpu-adv"
+DSTAT_OPTS="-tcmndrylp --top-cpu-adv"
 if [[ -n ${SCREEN_LOGDIR} ]]; then
     screen_it dstat "cd $TOP_DIR; dstat $DSTAT_OPTS | tee $SCREEN_LOGDIR/$DSTAT_FILE"
 else