pgsql: Code review for bigint-LIMIT patch.

Log Message:
-----------
Code review for bigint-LIMIT patch. Fix missed planner dependency,
eliminate unnecessary code, force initdb because stored rules change
(limit nodes are now supposed to be int8 not int4 expressions).
Update comments and error messages, which still all said 'integer'.

Modified Files:
--------------
pgsql/src/backend/executor:
nodeLimit.c (r1.26 -> r1.27)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeLimit.c.diff?r1=1.26&r2=1.27)
pgsql/src/backend/optimizer/plan:
planagg.c (r1.18 -> r1.19)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/plan/planagg.c.diff?r1=1.18&r2=1.19)
planner.c (r1.204 -> r1.205)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/plan/planner.c.diff?r1=1.204&r2=1.205)
pgsql/src/backend/parser:
parse_clause.c (r1.154 -> r1.155)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_clause.c.diff?r1=1.154&r2=1.155)
parse_coerce.c (r2.142 -> r2.143)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_coerce.c.diff?r1=2.142&r2=2.143)
pgsql/src/include/catalog:
catversion.h (r1.340 -> r1.341)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h.diff?r1=1.340&r2=1.341)
pgsql/src/include/nodes:
parsenodes.h (r1.317 -> r1.318)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/parsenodes.h.diff?r1=1.317&r2=1.318)
plannodes.h (r1.83 -> r1.84)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/plannodes.h.diff?r1=1.83&r2=1.84)
pgsql/src/include/parser:
parse_coerce.h (r1.64 -> r1.65)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/parser/parse_coerce.h.diff?r1=1.64&r2=1.65)