7842 - new directory organization

Baremetal is now the default build target and therefore has its sources
at the top-level. Baremetal programs build using the phase-2 Mu toolchain
that requires a Linux kernel. This phase-2 codebase which used to be at
the top-level is now under the linux/ directory. Finally, the phase-2 toolchain,
while self-hosting, has a way to bootstrap from a C implementation, which
is now stored in linux/bootstrap. The bootstrap C implementation uses some
literate programming tools that are now in linux/bootstrap/tools.

So the whole thing has gotten inverted. Each directory should build one
artifact and include the main sources (along with standard library). Tools
used for building it are relegated to sub-directories, even though those
tools are often useful in their own right, and have had lots of interesting
programs written using them.

A couple of things have gotten dropped in this process:
  - I had old ways to run on just a Linux kernel, or with a Soso kernel.
    No more.
  - I had some old tooling for running a single test at the cursor. I haven't
    used that lately. Maybe I'll bring it back one day.

The reorg isn't done yet. Still to do:
  - redo documentation everywhere. All the README files, all other markdown,
    particularly vocabulary.md.
  - clean up how-to-run comments at the start of programs everywhere
  - rethink what to do with the html/ directory. Do we even want to keep
    supporting it?

In spite of these shortcomings, all the scripts at the top-level, linux/
and linux/bootstrap are working. The names of the scripts also feel reasonable.
This is a good milestone to take stock at.

1 files changed, 33 insertions, 0 deletions

diff --git a/linux/tile/README.md b/linux/tile/README.md
new file mode 100644
index 00000000..a13f7662
--- /dev/null
+++ b/linux/tile/README.md
@@ -0,0 +1,33 @@
+A programming environment that tries to [“stop drawing dead fish”](http://worrydream.com/#!/StopDrawingDeadFish).
+
+<img alt='screenshot' src='../../html/rpn5.png' width='500px'>
+
+To run:
+
+```
+./translate_mu apps/tile/*.mu
+./a.elf screen
+```
+
+To run tests:
+
+```
+./a.elf test
+```
+
+To run a conventional REPL (for debugging):
+
+```
+./a.elf type
+```
+
+## hacking
+
+Unlike the top-level directory, this is just a prototype so far. There are no
+tests.
+
+To add a new primitive you'll need to hard-code it into the `evaluate`
+function (apps/tile/rpn.mu).
+
+There's also a second place you'll want to teach about predefined primitives:
+`bound-function?` (apps/tile/environment.mu)