Add deprecation note

README.md

@@ -1,24 +1,3 @@
-This is a small (under-300-line) stub that you can import into your Rust
-projects to create almost completely freestanding Rust programs. The only
-dependencies are the following libc functions: `malloc`, `free`, `abort`,
-`memcpy`, and `memcmp`. See `hello.rs` for an example of usage.
-
-With a small modification, you could implement syscalls (via inline assembly)
-and an allocator yourself to avoid the dependencies on these functions. This
-was not done in the interests of simplicity.
-
-Unfortunately, a couple of runtime functions still have to be around, although
-they are never called in the resulting programs. They could be stubbed out.
-This should be considered a Rust bug.
-
-Garbage collection, tasks, and failure will not work. All the other language
-features, including unique pointers, references, and closures *do* work, so
-programs such as sprocketnes that do not use garbage collection should be
-fine.
-
-The Rust standard library cannot be used in this mode, but splitting out the
-Rust standard library into a portion that can be used in freestanding mode
-would be an interesting and valuable project (IMO).
-
-As with the rest of Rust, this should not be considered production-ready.
+This is *deprecated* and is no longer maintained. It is no longer necessary to use this to achieve
+runtime-less operation; just use `#[start]` and/or `#[no_std]` and avoid the runtime.