pgsql: Add stats functions and views to provide access to a

Log Message:
-----------
Add stats functions and views to provide access to a transaction's own
statistics counts.  These numbers are being accumulated but haven't yet been
transmitted to the collector (and won't be, until the transaction ends).
For some purposes, though, it's handy to be able to look at them.

Joel Jacobson, reviewed by Itagaki Takahiro

Modified Files:
--------------
    pgsql/doc/src/sgml:
        monitoring.sgml (r1.81 -> r1.82)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/monitoring.sgml?r1=1.81&r2=1.82)
    pgsql/src/backend/catalog:
        system_views.sql (r1.66 -> r1.67)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/system_views.sql?r1=1.66&r2=1.67)
    pgsql/src/backend/postmaster:
        pgstat.c (r1.204 -> r1.205)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/pgstat.c?r1=1.204&r2=1.205)
    pgsql/src/backend/utils/adt:
        pgstatfuncs.c (r1.60 -> r1.61)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/pgstatfuncs.c?r1=1.60&r2=1.61)
    pgsql/src/include/catalog:
        catversion.h (r1.591 -> r1.592)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h?r1=1.591&r2=1.592)
        pg_proc.h (r1.575 -> r1.576)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h?r1=1.575&r2=1.576)
    pgsql/src/include:
        pgstat.h (r1.89 -> r1.90)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/pgstat.h?r1=1.89&r2=1.90)
    pgsql/src/test/regress/expected:
        rules.out (r1.155 -> r1.156)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/rules.out?r1=1.155&r2=1.156)