Functon no longer supported. Why?

Hello,
Could anyone explain why the following is no longer supported by default.
Now I have to write a function upper(inet).
I have a script which suddenly stop working after the upgrade:)))

I just want to know why:)
Kaloyan

template1=# select version();

version
---------------------------------------------------------------------------------------------------------
 PostgreSQL 7.4.1 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 3.3.2
(Mandrake Linux 10.0 3.3.2-6mdk)
(1 row)

template1=# select upper('193.68.13.6'::inet);
ERROR:  function upper(inet) does not exist
HINT:  No function matches the given name and argument types. You may
need to add explicit type casts.

=====================================================================
libvar=# select upper('193.68.13.6'::inet);
     upper
----------------
 193.68.13.6/32
(1 row)

libvar=# select version();
                            version
----------------------------------------------------------------
 PostgreSQL 7.2.3 on i386-pc-bsdi4.0.1, compiled by GCC 2.7.2.1
(1 row)