Give crafts unique ids in the form of a type+id tuple. Since we can now safely hold "weak pointers" to crafts, let UFOs refer to their killer by unique id, instead of a pointer that may be deallocated or reused
Provide a savegame method to look up a craft by its unique id, it could always come in handy
`typedef std::pair<std::string, int> CraftId` to make code more readable
Downgrade C++11 code: no `auto`, no for-each loops
Fix indentation (use tabs)
`nullptr` → `NULL`
Forgot to commit this file
Removed unnecessary `#include`
Finishing touches
Merge pull request #943 from hackbunny/unique_craft_ids_redux

Give crafts unique ids in the form of a type+id tuple