docs:  specify FOR UPDATE/SHARE incompatibilities
docs:  specify FOR UPDATE/SHARE incompatibilities

Document that FOR UPDATE/SHARE are incompatible with GROUP BY, DISTINCT,
HAVING and window functions.

Michael Paquier

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