busybox

Second drop.  More infrastructure in place, especially for parsing pipelines.
The minimal version got a couple hundred bytes bigger, partly because it's
broken into more functions but mostly because it now dynamically reallocates
and frees everything with no hard-coded limits.  (I thought about making
that optional, but there's a limit to what I can debug and maintain.  It
should still be reasonably NOMMU friendly, the allocations are small and
short lived, and shouldn't contribute noticeably to long-term memory
fragmentation.)