This is a workaround for lovely boost 1.48 incompatibility causing compile errors on assignment to StrSet from a temporary StrSet, see https://svn.boost.org/trac/boost/ticket/6167 for more details.

It would create one only if top-level parse_match_operator
parser rule had been used. Now it creates it within
match_rule_operator parser rule, so it works for parse_wccl_file
as well.

Allows for application of all rules on an annotated sequence
via apply_all method.

It was returning Position based off absolute position, which
was no good for operators like orth[first(M)] working in changing
sentence contexts.

This reflects the fact that positions stored in matches are
absolute positions, while Position type is used in the
language as position relative to current position in the
sentence context. So mixing the two was confusing at the very least.
This also actually fits the most recent version of spec,
which no longer mentions Position, either.