Make use C++11 union (saves around 8 bytes per instance)
language: Structure-pack most used types
Make use of C++11 typed-enums and C++11 unions
sizeof-statistics (64 bit system):
- DUChainBaseData: 24B -> 20B
- AbstractTypeData: 32B -> 12B
- DelayedTypeData: 40B -> 24B
- DeclarationData: 76B -> 60B
- DUContextData: 64B -> 56B
- TopDUContextData: 96B -> 80B (not instantiated *that* often)