SF bug 480215: softspace confused in nested print

This fixes the symptom, but PRINT_ITEM has no way to know what (if
anything) PyFile_WriteObject() writes unless the object being printed
is a string.  When the object isn't a string, this fix retains the
guess that softspace should be set after PyFile_WriteObject().
We might want to say that it's the job of filelike-object write methods
to leave the file's softspace in the correct state.  That would probably
be better -- but everyone relies on PRINT_ITEM to guess for them now.