[plt-dev] a common collection for utility modules

I propose to add a new collection called "unstable" to serve as a  
place to put small libraries that might be of general use but either  
don't fit or aren't ready for any of the existing locations. For  
example, a graph traversal algorithm using an idiosyncratic list-based  
graph representation doesn't fit in scheme/list, and it isn't  
significant or general enough to justify creating scheme/graph. But it  
might be useful to more than the one module that currently uses it.

There are 62 files in the collection tree ending in either "util.ss"  
or "utils.ss". At least some of that code must be useful to more than  
one client.

The name "unstable" is intended as a warning that the *interfaces* in  
particular are unstable. Developers of planet packages and external  
projects should avoid using modules in the unstable collection.  
Contracts may change, names may change or disappear, even entire  
modules may move or disappear without warning to the outside world. Of  
course, people who make changes to modules in unstable must fix up any  
uses within the collections tree.

I hope the unstable collection will lead to more code sharing. I also  
hope that it will be a place to hash out interfaces and get  
implementations Just Right before promoting code to the major  
leagues^W collections. Not for all code, just for code that doesn't  
immediately fit in anywhere else.

Ryan