This change is specifically aimed at code objects.
As it is, it is impossible to produce code objects that share common data (e.g. filename strings, common tuples, name strings, etc) that don't unserialize to separate objects.

Also, separately but related (see second patch) the effort spent in interning names when compiling, is lost when code objects are loaded back from disk.

This change is based on work done at CCP to reduce the size of compiled code in memory.  Simple preprocessing of code objects prior to writing them to disk can result in important memory savings.