orafce - orafce: replace not necessery stable attr with immutable

Log Message:
-----------
replace not necessery stable attr with immutable

Modified Files:
--------------
orafce:
orafunc.sql.in (r1.27 -> r1.28)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/orafce/orafce/orafunc.sql.in.diff?r1=1.27&r2=1.28)
plvdate.c (r1.7 -> r1.8)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/orafce/orafce/plvdate.c.diff?r1=1.7&r2=1.8)