Mem leak fix in uthreads

[Will Ware]

Jeff Collins identified and fixed some memory leaks in my
microthreads package. The patched version is available at
ftp://ftp.std.com/pub/wware/uthreads.tgz.

I am hoping before the conference to make some progress on
merging microthreads with Christian Tismer's Stackless Python.
Things are a bit busy but I'll see what I can do.
-- 
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 22nd century: Esperanto, geodesic | Will Ware
 domes, hovercrafts, metric system | wware at world.std.com