Separated lookahead tags from tag versions in closure items.

Separated lookahead tags from tag versions in closure items.

This commit reverts commit 0b2ca9bf141259baf6cb0b067621c06db5f06b46:
"Pack lookahead tags together with tag versions in TDFA state."

Packing was possible because we were not interested in tag version
if closure item had this tag in lookahead set. However, if we are
to store the full history of each tag, we'll need this intermediate
version in spite of the fact that it is overwritten on the next
transition.