pgsql: Remove grammar productions for prefix and postfix % and ^

Log Message:
-----------
Remove grammar productions for prefix and postfix % and ^ operators,
as well as the existing pg_catalog entries for prefix and postfix %.
These have never been documented, though they did appear in one old
regression test. This avoids surprising behavior in cases like
"SELECT -25 % -10". Per recent discussion.
Note: although there is a catalog change here, I did not force initdb
since there's no harm in leaving the inaccessible entries in one's
copy of pg_operator.

Modified Files:
--------------
pgsql/doc/src/sgml/ref:
comment.sgml (r1.28 -> r1.29)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/comment.sgml.diff?r1=1.28&r2=1.29)
pgsql/src/backend/parser:
gram.y (r2.491 -> r2.492)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/gram.y.diff?r1=2.491&r2=2.492)
pgsql/src/include/catalog:
pg_operator.h (r1.132 -> r1.133)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_operator.h.diff?r1=1.132&r2=1.133)
pgsql/src/test/regress/expected:
float8-exp-three-digits-win32.out (r1.6 -> r1.7)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/float8-exp-three-digits-win32.out.diff?r1=1.6&r2=1.7)
float8-exp-three-digits.out (r1.11 -> r1.12)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/float8-exp-three-digits.out.diff?r1=1.11&r2=1.12)
float8-small-is-zero.out (r1.9 -> r1.10)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/float8-small-is-zero.out.diff?r1=1.9&r2=1.10)
float8-small-is-zero_1.out (r1.3 -> r1.4)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/float8-small-is-zero_1.out.diff?r1=1.3&r2=1.4)
float8.out (r1.23 -> r1.24)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/float8.out.diff?r1=1.23&r2=1.24)
pgsql/src/test/regress/sql:
float8.sql (r1.14 -> r1.15)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/float8.sql.diff?r1=1.14&r2=1.15)