Add a note to PG_TRY's documentation about volatile safety.
Add a note to PG_TRY's documentation about volatile safety.

We had better memorialize what the actual requirements are for this.

jmcatamney/gpdb,lisakowen/gpdb,pavanvd/postgres-xl,50wu/gpdb,ashwinstar/gpdb,50wu/gpdb,Postgres-XL/Postgres-XL,adam8157/gpdb,Postgres-XL/Postgres-XL,adam8157/gpdb,adam8157/gpdb,greenplum-db/gpdb,oberstet/postgres-xl,techdragon/Postgres-XL,50wu/gpdb,50wu/gpdb,adam8157/gpdb,xinzweb/gpdb,ashwinstar/gpdb,lisakowen/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,zeroae/postgres-xl,oberstet/postgres-xl,jmcatamney/gpdb,lisakowen/gpdb,techdragon/Postgres-XL,yazun/postgres-xl,xinzweb/gpdb,lisakowen/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,xinzweb/gpdb,lisakowen/gpdb,50wu/gpdb,ovr/postgres-xl,greenplum-db/gpdb,adam8157/gpdb,adam8157/gpdb,pavanvd/postgres-xl,oberstet/postgres-xl,greenplum-db/gpdb,techdragon/Postgres-XL,jmcatamney/gpdb,zeroae/postgres-xl,ovr/postgres-xl,pavanvd/postgres-xl,greenplum-db/gpdb,50wu/gpdb,yazun/postgres-xl,ashwinstar/gpdb,zeroae/postgres-xl,xinzweb/gpdb,ovr/postgres-xl,jmcatamney/gpdb,Postgres-XL/Postgres-XL,adam8157/gpdb,yazun/postgres-xl,greenplum-db/gpdb,ashwinstar/gpdb,ashwinstar/gpdb,50wu/gpdb,yazun/postgres-xl,techdragon/Postgres-XL,lisakowen/gpdb,greenplum-db/gpdb,oberstet/postgres-xl,xinzweb/gpdb,jmcatamney/gpdb,lisakowen/gpdb,xinzweb/gpdb,jmcatamney/gpdb,zeroae/postgres-xl,techdragon/Postgres-XL,adam8157/gpdb,pavanvd/postgres-xl,pavanvd/postgres-xl,oberstet/postgres-xl,50wu/gpdb,yazun/postgres-xl,ashwinstar/gpdb,greenplum-db/gpdb,Postgres-XL/Postgres-XL,lisakowen/gpdb,Postgres-XL/Postgres-XL,ovr/postgres-xl,ashwinstar/gpdb,ovr/postgres-xl,xinzweb/gpdb,xinzweb/gpdb,zeroae/postgres-xl