[cmucl-imp] New directory structure

[Raymond Toy]

Currently when you clone cmucl, you get a directory structure like

cmucl/
  BUILDING
  assembly/
  code/
  compiler/
  tools/
  <etc>

I want to change the structure to be

cmucl/
  BUILDING
  bin/
    build.sh
    build-all.sh
    create-target.sh
  src/

This is much convenient when using git.   It might be possible to
rearrange things even more, but I think this is good enough.  I'm tired
of having to cd to src to git diffs and logs and such.  With this
structure, I don't have to anymore.

Ray