pgsql: Revise pgstats stuff to fix the problems with not counting

Log Message:
-----------
Revise pgstats stuff to fix the problems with not counting accesses
generated by bitmap index scans.  Along the way, simplify and speed up
the code for counting sequential and index scans; it was both confusing
and inefficient to be taking care of that in the per-tuple loops, IMHO.
initdb forced because of internal changes in pg_stat view definitions.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        monitoring.sgml (r1.28 -> r1.29)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/monitoring.sgml.diff?r1=1.28&r2=1.29)
    pgsql/src/backend/access/gist:
        gistget.c (r1.51 -> r1.52)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gist/gistget.c.diff?r1=1.51&r2=1.52)
    pgsql/src/backend/access/hash:
        hashsearch.c (r1.38 -> r1.39)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/hash/hashsearch.c.diff?r1=1.38&r2=1.39)
    pgsql/src/backend/access/heap:
        heapam.c (r1.198 -> r1.199)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/heap/heapam.c.diff?r1=1.198&r2=1.199)
    pgsql/src/backend/access/index:
        indexam.c (r1.84 -> r1.85)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/index/indexam.c.diff?r1=1.84&r2=1.85)
    pgsql/src/backend/access/nbtree:
        nbtsearch.c (r1.93 -> r1.94)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtsearch.c.diff?r1=1.93&r2=1.94)
    pgsql/src/backend/access/rtree:
        rtget.c (r1.35 -> r1.36)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/rtree/rtget.c.diff?r1=1.35&r2=1.36)
    pgsql/src/backend/catalog:
        system_views.sql (r1.21 -> r1.22)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/system_views.sql.diff?r1=1.21&r2=1.22)
    pgsql/src/backend/executor:
        nodeBitmapHeapscan.c (r1.2 -> r1.3)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeBitmapHeapscan.c.diff?r1=1.2&r2=1.3)
    pgsql/src/backend/postmaster:
        pgstat.c (r1.108 -> r1.109)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/pgstat.c.diff?r1=1.108&r2=1.109)
    pgsql/src/include/catalog:
        catversion.h (r1.303 -> r1.304)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h.diff?r1=1.303&r2=1.304)
    pgsql/src/include:
        pgstat.h (r1.36 -> r1.37)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/pgstat.h.diff?r1=1.36&r2=1.37)
    pgsql/src/include/utils:
        rel.h (r1.85 -> r1.86)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/rel.h.diff?r1=1.85&r2=1.86)
    pgsql/src/test/regress/expected:
        rules.out (r1.108 -> r1.109)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/rules.out.diff?r1=1.108&r2=1.109)
        stats.out (r1.5 -> r1.6)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/stats.out.diff?r1=1.5&r2=1.6)
    pgsql/src/test/regress/sql:
        stats.sql (r1.3 -> r1.4)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/stats.sql.diff?r1=1.3&r2=1.4)