Reflection of types with non-trivial literal template arguments does not work

[fabian-jung]

For example reflection of std::array will not work, because it takes an std::size_t, as second template argument and std::size_t is not known, when first used in the generated code.

To fix this the (forward) definition for these types must be generated and placed before the first use.

is included in reflection.hpp as a workaround. This can be removed if the issue is fixed.