bugfix - VIP: variadic function ignore strict flag

Hello,

I am returning back to message
http://archives.postgresql.org/pgsql-general/2010-02/msg00119.php

Our implementation of variadic parameters missing correct handling
test on NULL, and test on non constant value.

This patch add correct tests for variadic parameters. Probably
Gen_fmgrtab.pl have needs some work - there are magic constants for
InvalidOid and ANYOID.

Regards

Pavel Stehule