pgsql: Allow units to be specified with configuration settings.

Log Message:
-----------
Allow units to be specified with configuration settings.

Modified Files:
--------------
pgsql/doc/src/sgml:
catalogs.sgml (r2.127 -> r2.128)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/catalogs.sgml.diff?r1=2.127&r2=2.128)
config.sgml (r1.70 -> r1.71)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/config.sgml.diff?r1=1.70&r2=1.71)
pgsql/src/backend/catalog:
system_views.sql (r1.28 -> r1.29)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/system_views.sql.diff?r1=1.28&r2=1.29)
pgsql/src/backend/utils/misc:
guc-file.l (r1.37 -> r1.38)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc-file.l.diff?r1=1.37&r2=1.38)
guc.c (r1.331 -> r1.332)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc.c.diff?r1=1.331&r2=1.332)
pgsql/src/bin/initdb:
initdb.c (r1.118 -> r1.119)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/initdb/initdb.c.diff?r1=1.118&r2=1.119)
pgsql/src/include/utils:
guc_tables.h (r1.23 -> r1.24)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/guc_tables.h.diff?r1=1.23&r2=1.24)
pgsql/src/test/regress/expected:
rules.out (r1.116 -> r1.117)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/rules.out.diff?r1=1.116&r2=1.117)