tree2scop.c: scop_from_affine_for: delay construction of condition pet_scop

tree2scop.c: scop_from_affine_for: delay construction of condition pet_scop

We want to change the extraction of a pet_scop from a pet_tree
from a bottom-up to a top-down process.
In particular, we want to pass down the domain information derived
from outer constructs to inner constructs.  This means we have
to construct the pet_scop for the non-affine condition (if any)
after the domain has been constructed, but still before the pet_scop
for the body is constructed.

Signed-off-by: Sven Verdoolaege <skimo@kotnet.org>