Add optional comments strings in CL style to macro definitions

Currently these are just ignored but in the future we will keep them.
Add more a-list functions to predefined library

Add functions pairlis, (r)assoc-if, (r)assoc-if-not and sublis.
Fix indenting of known forms when no depth limit

The pretty printer did not correctly handle the case when there was no
depth limit and just ignored the rules.