ia64 "hello world" success; crfsd receives SEGV under heavier load

[Zach Brown]

> #3  0x2000000000084180 in __assert_fail () from /lib/tls/libc.so.6.1

>     at crfsd/update.c:868

I think I fixed this:

  http://oss.oracle.com/mercurial/zab/crfs/rev/f163aed9f781

The log showed that right before the assertion failure we split a child
and took up the last block pointer slot in the parent.  The assertion
didn't take this case into account.

- z