Add control over whether fast integer lookups are created

std/cpp/rtti/FieldIntegerLookup.hx

@@ -0,0 +1,8 @@
+package cpp.rtti;
+
+/**
+	If you implement this interface, then the backend will generate code that
+	allows fast dynamic access to fields by integer id.  This should speed up the CFFI.
+**/
+interface FieldIntegerLookup {
+}

std/cpp/rtti/FieldNumericIntegerLookup.hx

@@ -0,0 +1,8 @@
+package cpp.rtti;
+
+/**
+	If you implement this interface, then the backend will generate code that
+	allows fast numeric access to fields by integer id.  This should speed up the CFFI.
+**/
+interface FieldNumericIntegerLookup {
+}