Remove incorrect commented out code

Mark commented out code as unused

plpython: Streamline initialization

plpython: Remove duplicate PyModule_Create()

plpython: Clean up PyModule_AddObject() uses

plpython: Remove commented out code

Change some Datum to void * for opaque pass-through pointer

Remove MsgType type

Remove useless casts in format arguments

Clean up int64-related format strings

Remove unnecessary casts in printf format arguments (%zu/%zd)

Use PGAlignedXLogBlock for some code simplification