Add functionality to generate a wrapper library. A wrapper library includes:
1. entry points
2. dispatch table (accessed from the library entry points)
3. dispatch table accessor callback
4. dispatch table initialization function
Note that the dispatch table initialization function used to be part of the decoder. This
change moves it to be part of the dispatch table layer where it belongs.
Change-Id: Ide6764a17cc029056f9946e778a513cdc2a49003
ea3a3584f5