Oracle: Init parameter _ORACLE_SCRIPT

Scripts maintained under $ORACLE_HOME use $ORACLE_HOME/rdbms/admin/sqlsessstart.sql and sqlsessend.sql to set the value of _oracle_script to true or false.

A comment found in $ORACLE_HOME/md/admin/catmd.sql indicates that setting the value of _oracle_script to true prior to creating an object marks that object as Oracle-supplied.