pgsql: Clean up the INET-vs-CIDR situation.

Log Message:
-----------
Clean up the INET-vs-CIDR situation.  Get rid of the internal is_cidr flag
and rely exclusively on the SQL type system to tell the difference between
the types.  Prevent creation of invalid CIDR values via casting from INET
or set_masklen() --- both of these operations now silently zero any bits
to the right of the netmask.  Remove duplicate CIDR comparison operators,
letting the type rely on the INET operators instead.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        func.sgml (r1.302 -> r1.303)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml.diff?r1=1.302&r2=1.303)
    pgsql/src/backend/optimizer/path:
        indxpath.c (r1.197 -> r1.198)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/path/indxpath.c.diff?r1=1.197&r2=1.198)
    pgsql/src/backend/utils/adt:
        network.c (r1.60 -> r1.61)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/network.c.diff?r1=1.60&r2=1.61)
    pgsql/src/include/catalog:
        catversion.h (r1.312 -> r1.313)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h.diff?r1=1.312&r2=1.313)
        pg_amop.h (r1.67 -> r1.68)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_amop.h.diff?r1=1.67&r2=1.68)
        pg_cast.h (r1.24 -> r1.25)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_cast.h.diff?r1=1.24&r2=1.25)
        pg_operator.h (r1.137 -> r1.138)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_operator.h.diff?r1=1.137&r2=1.138)
        pg_proc.h (r1.392 -> r1.393)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h.diff?r1=1.392&r2=1.393)
    pgsql/src/include/utils:
        builtins.h (r1.271 -> r1.272)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/builtins.h.diff?r1=1.271&r2=1.272)
        inet.h (r1.21 -> r1.22)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/inet.h.diff?r1=1.21&r2=1.22)
    pgsql/src/test/regress/expected:
        opr_sanity.out (r1.61 -> r1.62)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/opr_sanity.out.diff?r1=1.61&r2=1.62)
    pgsql/src/test/regress/sql:
        opr_sanity.sql (r1.48 -> r1.49)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/opr_sanity.sql.diff?r1=1.48&r2=1.49)