[plt-scheme] likely 3.99.0.22 -> 3.99.0.23 incompatibility: hash tables

All the changes you list sound good to me.  Two minor questions of 
rationale, perhaps worth documenting:

1. Why do mutable hash tables *not* support the functional operations?  
Of course mutable lists have supported functional "append" just as 
immutable lists do, for example.

2. Why is the "hash-table-set" not the more generic "table-set"?  Can't 
*all* tables have keyed values set functionally (especially given that 
there is a "table-set!" that implies all mutable tables can have values 
set via mutation)?

-- 
http://www.neilvandyke.org/