Fix some tests and do some cleanup.

test/pass_and_access_struct_fields_in_functions.inx

@@ -0,0 +1,13 @@
+Foo :: struct {
+	some_data : float;
+}
+
+foo :: (f : Foo) -> float {
+	return f.some_data * 2.0;
+}
+
+vertex main :: () {
+	f : Foo;
+	f.some_data = 4.0;
+	d : float = foo(f);
+}