Switched to a simpler concept, see below.
Switched to a simpler concept, see below.

Spans are now active until they reach a certail utilization bound, which makes
them inactive and reusable (stealing, local reusable).

Signed-off-by: Michael Lippautz <0d543840881a2c189b4f7636b15eebd6a8f60ace@gmail.com>

cksystemsgroup/scalloc,cksystemsgroup/scalloc,cksystemsgroup/scalloc