These aren't used for anything yet, but should be useful for stable IDs
when printing nodes before and after passes and for faster cycle
detection than the current map of pointers.
We want to use the fully qualified name for scoped enums to keep the C++
compiler happy. When a parameter expects an enum value, we must supply
an enum value and not its underlying integer value.
Before:
isset_bitset<1, 0>
After:
isset_bitset<1, apache::thrift::detail::IssetBitsetOption::Unpacked>
When we were previously removing allocators, we were only able to work
with containers whose allocators appeared as their last template
parameter.
Now we can replace allocators in the middle of a parameter list.
This fixes tests for folly::sorted_vector_set.
This is necessary when replacing the allocator of a map type, for
example.
`std::map<int, int>` will need an allocator which allocates elements of
type `std::pair<const int, int>>`
