Fix build (accidentally copied class_info).
Fix build (accidentally copied class_info).

Commit 3be9a701e06d6cf6049831076c4b0187c66c8e70 removed explicit copy/move ctors
for apollo::detail::class_info, accidentally fixing the bug that the
implicit_ctors member was forgotten there. Turns out this makes class_info a
move-only class since implicit_ctors is a map containing unique_ptrs. For some
reason using brace initialization for std::pair causes the pair to be copied
instead of moved into the class registry on g++ 4.9.2 (works fine with MSVC14),
so use std::make_pair() instead.

Oberon00/apollo,Oberon00/apollo