Implement the while loop

tests/expectations/print_after_loop.txt

@@ -0,0 +1 @@
+2

tests/expectations/print_in_proc.txt

@@ -0,0 +1 @@
+14

tests/vm/print_after_loop.elna

@@ -0,0 +1,9 @@
+proc main() {
+  var x: int;
+
+  x := 0;
+  while (x < 2) {
+    x := x + 1;
+  }
+  printi(x);
+}

tests/vm/print_in_proc.elna

@@ -0,0 +1,7 @@
+proc print2(a: int) {
+  printi(a);
+}
+
+proc main() {
+  print2(14);
+}