pgAdmin III: adjust code as per new EDB AS90 functions/procedures semantics

Hi,

In EDBAS 9.0, following notable restructuring has been done with respect to
functions and procedures. We need to adopt the same in the pgAdmin code
base. Note that these changes make EDBAS funcs/procs behave more like native
Postgres functions which is a good thing:

* To debug edb-SPL functions/procedures, the debugger was using custom
EDB-protocol extension. With the latest refactorings, the normal code path
which was being employed for plpgsql objects can be used. This patch checks
for the version number at appropriate locations to avoid calling this custom
protocol now. Obviously the current behavior has to be retained for pre 9.0
versions. (changes in debugger files. Had to also make some misc. changes to
handle default parameters appropriately.)

* Procedures with or without OUT-parameters can now also be called without
the EDB-protocol extension with the EXEC command. For example, if you have a
procedure like "fooproc(a IN integer, b OUT integer)", you can call it with
"exec fooproc(123)". The OUT value is returned as the return value, just as
if it was a function call. Again this behaviour will now be the same as for
normal plpgsql objects.(pgFunction.cpp)

* If an SPL-function has both an OUT-parameter and a return value, the
return value is transformed into an extra OUT-parameter named "_retval_".
This patch adds code to identify such a column and use its type to set the
return type appropriately. (pgFunction.cpp)

Note that the changes are not as intensive as the above may sound. The
protocol extension was only being used by the debugger code paths, so the
changes are localised in that module. The remaining changes are in
pgFunction.cpp file only. I tested the debugger changes against both AS90
and AS84 code bases. For the latter the extended protocol is getting invoked
appropriately. No testing on windows though yet.

Regards,
Nikhils