Add extra tests.

These files aspects of bindgen behavior which may not be generally useful to
most consumers but are more important to downstream postprocessors such as
autocxx.

One of them tests enums embedded within classes, and the other tests various
types of C++ constructor.

Part of google/autocxx#124.

Author: adetaylor

bindgen-tests/tests/expectations/tests/class_with_enum.rs

@@ -0,0 +1,7 @@
+class A {
+public:
+    enum B {
+        B1,
+        B2,
+    };
+};

bindgen-tests/tests/expectations/tests/special-members.rs

@@ -0,0 +1,7 @@
+class A {
+public:
+    A();
+    A(A&);
+    A(A&&);
+    ~A();
+};