Enum clean-ups

Enum clean-ups

Generate enum types where appropriate.
Fix prototypes where a method took a "gint" that was really a bitflag.
Remove tables of state and role names, since these are now redundant with data
from the generated enums and would need to be maintained in parallel.

These changes were originally in master but have been backed out since they
break compatibility with pygobject 2.26.0, which some users are still using.