All of the current and future changes during shifting vtable functions
to MMD and deleting vtable entries may break existing PBCs. Any change
in the current classes enums, in MMD_<func> constants ... basically any
change in the generated runtime/parrot/include/*.pasm files.
I'll update PBC_COMPAT after these changes have settled once, probably
for 0.1.1 and add in some more comments, what actually breaks existing
PBCs. For now just be prepared that even small updates can still
invalidate existing byte code files without any notice.
leo
