pgsql-server: plpgsql does exceptions.

Log Message:
-----------
plpgsql does exceptions.
There are still some things that need refinement; in particular I fear
that the recognized set of error condition names probably has little in
common with what Oracle recognizes. But it's a start.

Modified Files:
--------------
pgsql-server/doc/src/sgml:
plpgsql.sgml (r1.41 -> r1.42)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/doc/src/sgml/plpgsql.sgml.diff?r1=1.41&r2=1.42)
pgsql-server/src/backend/access/transam:
xact.c (r1.173 -> r1.174)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/access/transam/xact.c.diff?r1=1.173&r2=1.174)
pgsql-server/src/include/access:
xact.h (r1.67 -> r1.68)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/access/xact.h.diff?r1=1.67&r2=1.68)
pgsql-server/src/include/utils:
errcodes.h (r1.13 -> r1.14)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/utils/errcodes.h.diff?r1=1.13&r2=1.14)
pgsql-server/src/pl/plpgsql/src:
gram.y (r1.57 -> r1.58)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/pl/plpgsql/src/gram.y.diff?r1=1.57&r2=1.58)
pl_exec.c (r1.108 -> r1.109)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/pl/plpgsql/src/pl_exec.c.diff?r1=1.108&r2=1.109)
pl_funcs.c (r1.32 -> r1.33)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/pl/plpgsql/src/pl_funcs.c.diff?r1=1.32&r2=1.33)
plpgsql.h (r1.47 -> r1.48)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/pl/plpgsql/src/plpgsql.h.diff?r1=1.47&r2=1.48)
pgsql-server/src/test/regress/expected:
plpgsql.out (r1.17 -> r1.18)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/test/regress/expected/plpgsql.out.diff?r1=1.17&r2=1.18)
pgsql-server/src/test/regress/sql:
plpgsql.sql (r1.12 -> r1.13)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/test/regress/sql/plpgsql.sql.diff?r1=1.12&r2=1.13)

Added Files:
-----------
pgsql-server/src/pl/plpgsql/src:
plerrcodes.h (r1.1)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/pl/plpgsql/src/plerrcodes.h?rev=1.1&content-type=text/x-cvsweb-markup)