Use sese_l throughout SCoP detection and create vec<scop_p> at the very end when
all SCoPs have been identified. 'struct sese_l' is very lightweight (two
pointers) compared to 'struct scop'.

No functional change intended. Passes regtest and bootstrap.

gcc/ChangeLog:

2015-10-01  Aditya Kumar  <hiraditya@msn.com>

        * graphite-scop-detection.c (struct sese_l): New conversion constructor
          so that this type can be pushed into a vec.
        (class scop_builder): use sese_l to collect scops.
        (get_scops): New getter function.
        (remove_intersecting_scops): Use sese_l instead of scops_p.
        (intersects): Same.
        (add_scop): Same.
        (subsumes): Same.
        (remove_subscops): Same.
        (build_scops): Add scops to vec<scops_p> once all the scops have been
        detected.

From-SVN: r228359