Don't split tag history into individual sub-histories for tags.

Don't split tag history into individual sub-histories for tags.

This is necassary for correct comparison of orbit tag histories:
if orbit tag is nested in an outer capture, this outer capture is
under repetition and there is an epsilon-path through it, then
this epsilon-path may contain pieces of orbit history that belong
to different iterations of outer capture; these pieces will be
glued together and the boundary between them will be lost.

Example: ((""){0,3}){0,2}.

However, in a common history we can always find boundaries
(they are marked by tags that correspond to outer captures).