Adjust stack size based on local variables

tests/expectations/two_variables.txt

@@ -0,0 +1,2 @@
+58
+28

tests/vm/two_variables.elna

@@ -0,0 +1,10 @@
+proc main() {
+  var i: int;
+  var j: int;
+
+  i := 58;
+  j := 28;
+
+  printi(i);
+  printi(j);
+}