fix: some analysis stage problems

tests/programs/neg_analyzer_continues_after_if_without_else.fzs

@@ -0,0 +1,9 @@
+fn choose(bool flag) int
+{
+  if (flag)
+    return 1;
+  return 0;
+}
+
+int invalid = "not an integer";
+exit(1);

tests/programs/pos_function_external_call.fzs

@@ -0,0 +1,12 @@
+fn doSomeWork()
+{
+  printline("Some work");
+}
+
+fn sum(int a, int b) int
+{
+  return a + b;
+}
+
+int result = sum(5, 6);
+printline(result);

tests/programs/pos_method_call_via_field.fzs

@@ -0,0 +1,19 @@
+class Node
+{
+  Node next;
+
+  fn ping()
+  {
+    printline("ping");
+  }
+
+  fn pingNext()
+  {
+    this.next.ping();
+  }
+}
+
+Node head = new Node;
+Node tail = new Node;
+head.next = tail;
+head.pingNext();