da.cc: include_other_source: only perform computations on single-valued filters
Since we are trying to derive information from the fact that some
iterations were not executed, we only know that there is some
filter element that lies outside the filter value. We can only
draw conclusions if exactly one element is accessed, i.e., if the
filter access relations are single-valued.
We therefore project out the filter access relations that are not
single-valued.
Signed-off-by: Sven Verdoolaege <skimo@kotnet.org>