Fix stack setting after error return. Some fixes to examples.

resources/examples/swap.c3

@@ -0,0 +1,20 @@
+module test;
+import libc;
+
+/**
+ * @checked a = b, b = a
+ */
+macro void @swap(&a, &b)
+{
+    $typeof(a) temp = a;
+    a = b;
+    b = temp;
+}
+
+fn void main()
+{
+	int x = 123;
+	int y = 456;
+	@swap(x, y);
+	libc::printf("x: %d y: %d\n", x, y);
+}