Add support for and_v(v:$sub1,$sub2) patterns

While 'or' in taptrees can easily be split into different leaves,
the same is not easily possible for policies that are composed
with a conjunction (except with DNF reductions that incur in an
exponential cost in the number of leaves, which is not practical).

This adds minimal support for matching pattern with disjunctive
policies, even just at a single level of nesting.

Author: bigspider