pgsql: Add support for dividing money by money (yielding a float8

Log Message:
-----------
Add support for dividing money by money (yielding a float8 result) and for
casting between money and numeric.

Andy Balholm, reviewed by Kevin Grittner

Modified Files:
--------------
    pgsql/doc/src/sgml:
        datatype.sgml (r1.250 -> r1.251)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/datatype.sgml?r1=1.250&r2=1.251)
    pgsql/src/backend/utils/adt:
        cash.c (r1.82 -> r1.83)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/cash.c?r1=1.82&r2=1.83)
    pgsql/src/include/catalog:
        catversion.h (r1.587 -> r1.588)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h?r1=1.587&r2=1.588)
        pg_cast.h (r1.44 -> r1.45)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_cast.h?r1=1.44&r2=1.45)
        pg_operator.h (r1.170 -> r1.171)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_operator.h?r1=1.170&r2=1.171)
        pg_proc.h (r1.571 -> r1.572)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h?r1=1.571&r2=1.572)
    pgsql/src/include/utils:
        cash.h (r1.27 -> r1.28)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/cash.h?r1=1.27&r2=1.28)