pgsql: Add Oracle-compatible GREATEST and LEAST functions.

Log Message:
-----------
Add Oracle-compatible GREATEST and LEAST functions. Pavel Stehule

Modified Files:
--------------
pgsql/doc/src/sgml:
func.sgml (r1.259 -> r1.260)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml.diff?r1=1.259&r2=1.260)
typeconv.sgml (r1.43 -> r1.44)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/typeconv.sgml.diff?r1=1.43&r2=1.44)
pgsql/src/backend/executor:
execQual.c (r1.179 -> r1.180)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/execQual.c.diff?r1=1.179&r2=1.180)
pgsql/src/backend/nodes:
copyfuncs.c (r1.308 -> r1.309)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/copyfuncs.c.diff?r1=1.308&r2=1.309)
equalfuncs.c (r1.245 -> r1.246)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/equalfuncs.c.diff?r1=1.245&r2=1.246)
outfuncs.c (r1.255 -> r1.256)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/outfuncs.c.diff?r1=1.255&r2=1.256)
readfuncs.c (r1.178 -> r1.179)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/readfuncs.c.diff?r1=1.178&r2=1.179)
pgsql/src/backend/optimizer/util:
clauses.c (r1.198 -> r1.199)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/util/clauses.c.diff?r1=1.198&r2=1.199)
pgsql/src/backend/parser:
gram.y (r2.497 -> r2.498)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/gram.y.diff?r1=2.497&r2=2.498)
keywords.c (r1.158 -> r1.159)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/keywords.c.diff?r1=1.158&r2=1.159)
parse_expr.c (r1.183 -> r1.184)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_expr.c.diff?r1=1.183&r2=1.184)
parse_target.c (r1.136 -> r1.137)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_target.c.diff?r1=1.136&r2=1.137)
pgsql/src/backend/utils/adt:
ruleutils.c (r1.200 -> r1.201)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/ruleutils.c.diff?r1=1.200&r2=1.201)
pgsql/src/include/nodes:
execnodes.h (r1.135 -> r1.136)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/execnodes.h.diff?r1=1.135&r2=1.136)
nodes.h (r1.170 -> r1.171)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/nodes.h.diff?r1=1.170&r2=1.171)
primnodes.h (r1.107 -> r1.108)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/primnodes.h.diff?r1=1.107&r2=1.108)
pgsql/src/pl/plpgsql/src:
pl_exec.c (r1.148 -> r1.149)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/pl_exec.c.diff?r1=1.148&r2=1.149)