This commit fixes the bug 3583921, datanode/coordinator slave crash.

This was caused by incorrect handling of KnownAssignedXids for XC,
where there could be missing Xids in WAL.   Now because XC does not
support consistent database view throught hot standby, KnownAssignedXids
are simply disabled.

Correct handling will be implemented when XC supports consistent
database view through hot standby.

	modified:   src/backend/storage/ipc/procarray.c
This commit improves the description of max_connections value at datanodes.

	modified:   doc-xc/src/sgml/installation.sgmlin
This commit improves gtm_ctl status behavior as described in the
reference manual.  Now for -Z gtm option, gtm_ctl status displays
if it runs as master or slave.

	modified:   src/bin/gtm_ctl/gtm_ctl.c
This is the fix for the bug 3600220 for REL1_0_STABLE, restart after
pg_ctl stop -m immediate.   Added unregistering the node from GTM
before postmaster finishes so that following pg_ctl start succeeds.

	modified:   src/backend/postmaster/postmaster.c
Disable FQS for all the OUTER joins

Patch by Ashutosh, I just did the commit
This is a improved patch to fix the bug 3600220.   Now there's no
additional action with -m immediate.   Coordinator/datanode will
remain registered to GTM.   Instead, when registration fails at
restart, it will try to unregister itself and then retry registration.

	modified:   src/backend/postmaster/postmaster.c
Remove an un-necessary loop while remote update planning.
Also the calls to make_remotequery while DML planning should pass a NIL plan target list.
Add comments on the need and usage of the flag non_fqs_dml in RemoteQueryState
Also correct a check in HandleCommandComplete
Fix for the bug 3553480.   Now gtm_ctl start in a shell script returns
if invoked with -l option.   This behavior is similar to pg_ctl.

	modified:   src/bin/gtm_ctl/gtm_ctl.c
Merge pull request #3 from postgres-xc/master

Pull from master