app_rpt: RPT_ALINKS / RPT_LINKS + associated l->links evalutation

[mkmer]

While we have addressed the string size for RPT_ALINKS and RPT_LINKS, l->links are still limited to [5120]-1 characters.

In a large network (somewhere around 510 nodes depending on node name sizes) a network node could receive a link list larger than 5120 which will be truncated.

While not critical, evaluation of how the strings are stored and alternative methods should be reviewed at some point.
Reference PR #474 and PR #470

[InterLinked1]

Personally, I think this is a great candidate for using an ast_str. A fixed size buffer for something that can vary with essentially no bounds doesn't seem appropriate here.