pgsql: Add support for tracking call counts and elapsed runtime for

Log Message:
-----------
Add support for tracking call counts and elapsed runtime for user-defined
functions.

Note that because this patch changes FmgrInfo, any external C functions
you might be testing with 8.4 will need to be recompiled.

Patch by Martin Pihlak, some editorialization by me (principally, removing
tracking of getrusage() numbers)

Modified Files:
--------------
pgsql/doc/src/sgml:
config.sgml (r1.177 -> r1.178)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/config.sgml?r1=1.177&r2=1.178)
monitoring.sgml (r1.58 -> r1.59)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/monitoring.sgml?r1=1.58&r2=1.59)
pgsql/src/backend/catalog:
system_views.sql (r1.51 -> r1.52)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/system_views.sql?r1=1.51&r2=1.52)
pgsql/src/backend/commands:
trigger.c (r1.233 -> r1.234)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/trigger.c?r1=1.233&r2=1.234)
vacuum.c (r1.373 -> r1.374)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/vacuum.c?r1=1.373&r2=1.374)
pgsql/src/backend/executor:
execQual.c (r1.230 -> r1.231)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/execQual.c?r1=1.230&r2=1.231)
pgsql/src/backend/postmaster:
autovacuum.c (r1.77 -> r1.78)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/autovacuum.c?r1=1.77&r2=1.78)
pgstat.c (r1.173 -> r1.174)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/pgstat.c?r1=1.173&r2=1.174)
pgsql/src/backend/tcop:
postgres.c (r1.552 -> r1.553)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/tcop/postgres.c?r1=1.552&r2=1.553)
pgsql/src/backend/utils/adt:
pgstatfuncs.c (r1.51 -> r1.52)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/pgstatfuncs.c?r1=1.51&r2=1.52)
pgsql/src/backend/utils/fmgr:
README (r1.12 -> r1.13)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/fmgr/README?r1=1.12&r2=1.13)
fmgr.c (r1.118 -> r1.119)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/fmgr/fmgr.c?r1=1.118&r2=1.119)
pgsql/src/backend/utils/misc:
guc.c (r1.453 -> r1.454)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc.c?r1=1.453&r2=1.454)
postgresql.conf.sample (r1.240 -> r1.241)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/postgresql.conf.sample?r1=1.240&r2=1.241)
pgsql/src/include/catalog:
catversion.h (r1.458 -> r1.459)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h?r1=1.458&r2=1.459)
pg_proc.h (r1.498 -> r1.499)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h?r1=1.498&r2=1.499)
pgsql/src/include:
fmgr.h (r1.58 -> r1.59)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/fmgr.h?r1=1.58&r2=1.59)
pgstat.h (r1.74 -> r1.75)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/pgstat.h?r1=1.74&r2=1.75)
pgsql/src/test/regress/expected:
rules.out (r1.138 -> r1.139)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/rules.out?r1=1.138&r2=1.139)
pgsql/src/include/portability:
instr_time.h (r1.1 -> r1.2)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/portability/instr_time.h?r1=1.1&r2=1.2)