This mostly involved frobbing imports between realstd, realcore, and the core
being test. Some of the imports are a little counterintuitive, but it mainly
focuses around libcore's types not implementing Show while libstd's types
implement Show.
Coherence requires that libcore's traits be implemented in libcore for ~[T] and
~str (due to them being language defined types). These implementations cannot
live in libcore forever, but for now, until Heap/Box/Uniq is a lang item, these
implementations must reside inside of libcore. While not perfect
implementations, these shouldn't reside in libcore for too long.
With some form of lang item these implementations can be in a proper crate
because the lang item will not be present in libcore.
