pgsql: Integrate autovacuum functionality into the backend.

Log Message:
-----------
Integrate autovacuum functionality into the backend. There's still a
few loose ends to be dealt with, but it seems to work. Alvaro Herrera,
based on the contrib code by Matthew O'Connor.

Modified Files:
--------------
pgsql/doc/src/sgml:
catalogs.sgml (r2.107 -> r2.108)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/catalogs.sgml.diff?r1=2.107&r2=2.108)
runtime.sgml (r1.337 -> r1.338)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/runtime.sgml.diff?r1=1.337&r2=1.338)
pgsql/src/backend/catalog:
Makefile (r1.55 -> r1.56)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/Makefile.diff?r1=1.55&r2=1.56)
pgsql/src/backend/commands:
analyze.c (r1.86 -> r1.87)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/analyze.c.diff?r1=1.86&r2=1.87)
vacuum.c (r1.310 -> r1.311)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/vacuum.c.diff?r1=1.310&r2=1.311)
vacuumlazy.c (r1.54 -> r1.55)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/vacuumlazy.c.diff?r1=1.54&r2=1.55)
pgsql/src/backend/postmaster:
Makefile (r1.20 -> r1.21)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/Makefile.diff?r1=1.20&r2=1.21)
pgstat.c (r1.99 -> r1.100)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/pgstat.c.diff?r1=1.99&r2=1.100)
postmaster.c (r1.458 -> r1.459)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/postmaster.c.diff?r1=1.458&r2=1.459)
pgsql/src/backend/tcop:
postgres.c (r1.453 -> r1.454)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/tcop/postgres.c.diff?r1=1.453&r2=1.454)
utility.c (r1.240 -> r1.241)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/tcop/utility.c.diff?r1=1.240&r2=1.241)
pgsql/src/backend/utils/init:
miscinit.c (r1.145 -> r1.146)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/init/miscinit.c.diff?r1=1.145&r2=1.146)
postinit.c (r1.152 -> r1.153)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/init/postinit.c.diff?r1=1.152&r2=1.153)
pgsql/src/backend/utils/misc:
guc.c (r1.273 -> r1.274)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc.c.diff?r1=1.273&r2=1.274)
postgresql.conf.sample (r1.152 -> r1.153)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/postgresql.conf.sample.diff?r1=1.152&r2=1.153)
pgsql/src/include/catalog:
catversion.h (r1.288 -> r1.289)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h.diff?r1=1.288&r2=1.289)
indexing.h (r1.89 -> r1.90)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/indexing.h.diff?r1=1.89&r2=1.90)
pgsql/src/include/commands:
vacuum.h (r1.59 -> r1.60)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/commands/vacuum.h.diff?r1=1.59&r2=1.60)
pgsql/src/include:
pgstat.h (r1.32 -> r1.33)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/pgstat.h.diff?r1=1.32&r2=1.33)
pgsql/src/include/tcop:
tcopprot.h (r1.75 -> r1.76)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/tcop/tcopprot.h.diff?r1=1.75&r2=1.76)
pgsql/src/include/utils:
guc_tables.h (r1.19 -> r1.20)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/guc_tables.h.diff?r1=1.19&r2=1.20)
pgsql/src/test/regress/expected:
sanity_check.out (r1.27 -> r1.28)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/sanity_check.out.diff?r1=1.27&r2=1.28)

Added Files:
-----------
pgsql/src/backend/postmaster:
autovacuum.c (r1.1)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/autovacuum.c?rev=1.1&content-type=text/x-cvsweb-markup)
pgsql/src/include/catalog:
pg_autovacuum.h (r1.1)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_autovacuum.h?rev=1.1&content-type=text/x-cvsweb-markup)
pgsql/src/include/postmaster:
autovacuum.h (r1.1)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/postmaster/autovacuum.h?rev=1.1&content-type=text/x-cvsweb-markup)