feat: add support for structs and member access

tests/struct_pointers.test

@@ -0,0 +1,38 @@
+[code]
+foreign fn putchar(c: i32) -> i32;
+
+struct Rect {
+    width: i32,
+    height: i32
+}
+
+fn modify_rect(r: *Rect) {
+    let temp: Rect = *r;
+    temp.width = temp.width + 10;
+    temp.height = temp.height + 20;
+    *r = temp;
+}
+
+fn print_num(n: i32) {
+    putchar(48 + (n / 10));
+    putchar(48 + (n % 10));
+    putchar(10);
+}
+
+fn main() -> i32 {
+    let r = Rect { width: 15, height: 25 };
+    
+    modify_rect(&r);
+    
+    print_num(r.width);
+    print_num(r.height);
+    
+    return 0;
+}
+
+[expected_return_code]
+0
+
+[expected_output]
+25
+45