Removes all references to blocks spawned during the parse, but does NOT delete them.
Call this function if you want to reuse the parser and you want to
delete all of the spawned blocks yourself (after calling ClearUsedBlockList() the DeleteBlocksFromFactories() function will not delete blocks)
Reimplemented from ExceptionRaisingNxsReader.
Definition at line 545 of file nxspublicblocks.h.