Solve Weak-vtables warning, improve memory use.

Having deque of pointers to objects of about uint32
was not really efficient, plus we had the "Weak-vtable"
warning.

keep everything in a union, manually resolve the right
function to call. Now we have a deque of operations.
Only block and reorder need further allocations.

Signed-off-by: Luca Fulchir <luker@fenrirproject.org>