[rt27912]
Add code to suppor on {commit expiry release} statements for DHCPv6.
There are several pieces to this change
1) Add space in the iasubopt structure to hold the statement pointers
2) Update the execute code to fill in the structures as necessary
3) Execute the statements when appropriate
Many of the changes in the non-v6 code are to pass the v6 structures
around to the execute code.
+- Add support for a simple check that the server id in a request message
+ to a failover peer matches the server id of the server. This support
+ is enabled by editing the file includes/site.h and uncommenting the
+ definition for SERVER_ID_CHECK. The option has several restrictions
+ and issues - please read the comment in the site.h file before
+ enabling it.
+ [ISC-Bugs #31463]
