add net draw script

tools/net.awk

+BEGIN {
+    print "digraph {"
+}
+/op:/ {
+    id++
+    op = $NF
+    opname = op "_" id
+    print opname "[\"label\"=\"" op " [" id "]" "\"]"
+}
+/input/ {
+    type = "input"
+}
+/output/ {
+    type = "output"
+}
+/argument/ {
+    if (type == "output") {
+        output[$NF] = opname
+    } else if (type == "input") {
+        if (output[$NF]) {
+            print output[$NF] " -> " opname
+        }
+    }
+}
+END {
+    print "}"
+}