compiled-file-name tries to put the .go in the %load-compiled-path

compiled-file-name tries to put the .go in the %load-compiled-path

* module/system/base/compile.scm (ensure-writable-dir): Rename from
  ensure-directory.
  (dsu-sort): Helper, does a decorate / sort / undecorate.
  (compiled-file-name): Refactor to only return a writable filename. The
  readable case is handled by load.c now, and the other case was silly.
  Hopefully it will do the right thing.
  (load-ensuring-compiled): Remove, load.c will call out to compile-file
  if necessary.
  (ensure-fallback-path): Remove, load.c will add the ~/.guile-ccache dir
  to the load-compiled path, which will prompt its creation if necessary.