Add a &inout style var-refs

A little confusing, because our regular
var expression is called variableReference
already ...

Plugins/Libraries/LighterCodeGenAST/Nodes/Expression.swift

@@ -194,7 +194,16 @@ public extension Expression {
   static func variable(_ name: String) -> Self {
     .variableReference(instance: nil, name: name)
   }
-
+
+  /// A variable (inout) reference, e.g. `&self.sql`.
+  static func variableRef(_ instance: String, _ name: String) -> Self {
+    .raw("&\(instance).\(name)") // TODO: add expr
+  }
+  /// A variable (inout) reference, e.g. `&self.sql`.
+  static func variableRef(_ name: String) -> Self {
+    .raw("&\(name)") // TODO: add expr
+  }
+
   /// A KeyPath expression.
   static func keyPath(_ baseType: TypeReference? = nil, _ property: String)
               -> Self