Updating changelog and docs for the new play_hosts variable

CHANGELOG.md

@@ -14,6 +14,7 @@ Major features/changes:
 * when using accelerate mode, the daemon will now be restarted when specifying a different remote_user between plays.
 * added no_log: option for tasks. When used, no logging information will be sent to syslog during the module execution.
 * acl module now handles 'default' and allows for either shorthand entry or specific fields per entry section
+* play_hosts is a new magic variable to provide a list of hosts in scope for the current play.
 
 
 New modules:

docsite/rst/playbooks_variables.rst

@@ -654,6 +654,8 @@ be useful for when you don't want to rely on the discovered hostname `ansible_ho
 reasons.  If you have a long FQDN, *inventory_hostname_short* also contains the part up to the first
 period, without the rest of the domain.
 
+*play_hosts* is available as a list of hostnames that are in scope for the current play. This may be useful for filling out templates with multiple hostnames or for injecting the list into the rules for a load balancer.
+
 Don't worry about any of this unless you think you need it.  You'll know when you do.
 
 Also available, *inventory_dir* is the pathname of the directory holding Ansible's inventory host file, *inventory_file* is the pathname and the filename pointing to the Ansible's inventory host file.