Cleanup AMPI DDT
Now that CkDDT confined to AMPI, we can remove the CkDDT constants and replace them directly with MPI_ constants.
That applies to the type names themselves "CkDDT_INT" -> "MPI_INT" and to return types "0" -> "MPI_SUCCESS".
Also DDT can be cleaned up with C++11 features '= default' such as ' = delete', and simple getter/setter routines could be moved into the header.
- Status changed from New to In Progress
Move simple routines and serialize() for primitive types into the header: https://charm.cs.illinois.edu/gerrit/#/c/charm/+/4152/