compact and much better one donated by Matt Dillon. Implement a simple
sbrk() which uses the existing setheap() api.
Remove the custom allocator from the UFS code. It wasn't working quite
right, and it shouldn't be needed with the new allocator.
Fix a serious problem with changing the value of already-existent
environment variables. Don't attempt to modify the supposedly-const
argument to putenv()
Fix an off-by-one sizing error in the zipfs code detected by the new
allocator.
Submitted by: zmalloc from Matt Dillon <dillon@backplane.com>
