Legacy codegeneration for immutable state variables.

test/libsolidity/semanticTests/immutable/external_function_pointer.sol

@@ -0,0 +1,20 @@
+contract D {
+    function f() external view returns (uint256) {
+        return 42;
+    }
+}
+contract C {
+    D d;
+    function() external view returns(uint256) immutable z;
+    constructor() public {
+        d = new D();
+        z = d.f;
+    }
+    function f() public view returns (uint256) {
+	assert(z.address == address(d));
+	assert(z.selector == D.f.selector);
+        return z();
+    }
+}
+// ----
+// f() -> 42

test/libsolidity/semanticTests/immutable/read_during_creation.sol

@@ -0,0 +1,13 @@
+contract C {
+    uint256 immutable x;
+    uint256 immutable y;
+    constructor() public {
+        x = 42;
+        y = x;
+    }
+    function f() public view returns (uint256, uint256) {
+        return (x+x,y);
+    }
+}
+// ----
+// f() -> 84, 42

test/libsolidity/semanticTests/immutable/stub.sol

@@ -0,0 +1,13 @@
+contract C {
+    uint256 immutable x;
+    uint256 immutable y;
+    constructor() public {
+        x = 42;
+        y = 23;
+    }
+    function f() public view returns (uint256, uint256) {
+        return (x+x,y);
+    }
+}
+// ----
+// f() -> 84, 23