pgsql: Fix breakage of bitmap scan plan creation for special index

Log Message:
-----------
Fix breakage of bitmap scan plan creation for special index operators such
as LIKE.  I oversimplified this code when removing support for plan-time
determination of index operator lossiness back in April --- I had thought
create_bitmap_subplan could stop returning two separate lists of qual
conditions, but it still must so that we can treat special operators
correctly in create_bitmap_scan_plan.  Per report from Rushabh Lathia.

Modified Files:
--------------
    pgsql/src/backend/optimizer/plan:
        createplan.c (r1.251 -> r1.252)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/plan/createplan.c?r1=1.251&r2=1.252)
    pgsql/src/test/regress/expected:
        btree_index.out (r1.5 -> r1.6)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/btree_index.out?r1=1.5&r2=1.6)
    pgsql/src/test/regress/sql:
        btree_index.sql (r1.5 -> r1.6)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/btree_index.sql?r1=1.5&r2=1.6)