some work to try to reduce the code size of some native libraries

- make sure that all binder Bn classes define a ctor and dtor in their respective library.
  This avoids duplication of the ctor/dtor in libraries where these objects are instantiated.
  This is also cleaner, should we want these ctor/dtor to do something one day.

- same change as above for some Bp classes and various other non-binder classes

- moved the definition of CHECK_INTERFACE() in IInterface.h instead of having it everywhere.

- improved the CHECK_INTERFACE() macro so it calls a single method in Parcel, instead of inlining its code everywhere

- IBinder::getInterfaceDescriptor() now returns a "const String16&" instead of String16, which saves calls to String16 and ~String16

- implemented a cache for BpBinder::getInterfaceDescriptor(), since this does an IPC. HOWEVER, this method never seems to be called.
  The cache makes BpBinder bigger, so we need to figure out if we need this method at all.
diff --git a/include/binder/BpBinder.h b/include/binder/BpBinder.h
index 067637e..7ef93aa 100644
--- a/include/binder/BpBinder.h
+++ b/include/binder/BpBinder.h
@@ -31,7 +31,7 @@
 
     inline  int32_t     handle() const { return mHandle; }
 
-    virtual String16    getInterfaceDescriptor() const;
+    virtual const String16&    getInterfaceDescriptor() const;
     virtual bool        isBinderAlive() const;
     virtual status_t    pingBinder();
     virtual status_t    dump(int fd, const Vector<String16>& args);
@@ -106,6 +106,7 @@
     };
 
             void                reportOneDeath(const Obituary& obit);
+            bool                isDescriptorCached() const;
 
     mutable Mutex               mLock;
             volatile int32_t    mAlive;
@@ -113,6 +114,7 @@
             Vector<Obituary>*   mObituaries;
             ObjectManager       mObjects;
             Parcel*             mConstantData;
+    mutable String16            mDescriptorCache;
 };
 
 }; // namespace android