Make talloc dependency optional

The idea is that some people might not actually have talloc.  In order
to avoid forcing them to depend on talloc I'm instead simply include a
version of talloc that I staticly link into pconfigure in this case.

There is still a dependency on clang here.  I think the best way to
avoid the clang dependency is to write a mini-clang (ie, call GCC's
dependency generator a few times) that I use when clang isn't
availiable.
Make Scala code fail when it fails

I was always "exit 0"ing in my wrapper code, I don't do that anymore.
Print Chisel debug output on failure

I was hiding this before because Scala files didn't actually fail
properly, but I can now show it!
Use zinc instead of scalac if possible

zinc is a new scalac replacement that support incremental compilation,
which makes scala builds a whole lot less painful.