Add a simple .aidl file
diff --git a/aidl/foo/IFoo.aidl b/aidl/foo/IFoo.aidl
new file mode 100644
index 0000000..cea4c1b
--- /dev/null
+++ b/aidl/foo/IFoo.aidl
@@ -0,0 +1,5 @@
+package foo;
+
+interface IFoo {
+	int add(int a, int b);
+}