Extracting more end-to-end tests.

test/libsolidity/semanticTests/structs/struct_reference.sol

@@ -0,0 +1,24 @@
+contract test {
+    struct s2 {
+        uint32 z;
+        mapping(uint8 => s2) recursive;
+    }
+    s2 data;
+    function check() public returns (bool ok) {
+        return data.z == 2 &&
+            data.recursive[0].z == 3 &&
+            data.recursive[0].recursive[1].z == 0 &&
+            data.recursive[0].recursive[0].z == 1;
+    }
+    function set() public {
+        data.z = 2;
+        mapping(uint8 => s2) storage map = data.recursive;
+        s2 storage inner = map[0];
+        inner.z = 3;
+        inner.recursive[0].z = inner.recursive[1].z + 1;
+    }
+}
+// ----
+// check() -> false
+// set() ->
+// check() -> true