Some structures needed to be cleaned for the reuse to be safe.
Reusing it cuts down on the overhead in lancebench.
Also uniqueness of block names are now enforced, and the common pattern
of "end_block blockName" could now be parsed if not always commented
out by begin_block handling.
Change-Id: I0daf6445292383aaab9392550d0842e0a654ad27
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>