tuned
removed Ids;
cleanup
added map_default, internal restructuring
AList.join now with 'DUP' exception
moved coalesce to AList, added equality predicates to library
clarified semantics of merge
added map_entry_yield
slight refinements
string_of_alist - convenient q'n'd printout function
added join
added merge, tuned
added make and find
added make function
better map_entry
added alist module