Introduce first groundwork for Wasm executor (#27)

* Introduce first groundwork for Wasm executor.

* Remove old Rust-runtime code.

* Avoid commiting compled files.

* Add runtime precompile.

* Rename so module makes more sense.

* Further renaming.

* Ensure tests work.

* Allow bringing in of externalities.

- Add util functions/macros.
- Add uncompacted runtime.
- Add some external crates from pwasm-std for managing allocs/memory
stuff.

* Nice macros for imports.

* Allow passing in of data through allocators.

Make memcpy and malloc work.
Basic allocator.

* Can now pass in bytes to WasmExecutor.

* Additional cleanup.

* Switch usages of `OutData` to `u64`

No need to be able to return bytes anymore.

* convert to safe but extremely verbose type conversion.

@rphmeier any more concise way of doing this?

* Remove StaticExternalities distinction.

* Remove another unused use.

* Refactor wasm utils out

* Remove extraneous copies that weren't really testing anything.

* Try to use wasm 0.15

* Make it work!

* Call-time externalities working.

* Add basic externalities.

* Fix grumbles and note unwraps to be sorted.

* Test storage externality.

Unforunately had to change signatures of externalities to avoid
immutable function returning a reference. Not sure what to do about
this...

* Fix nits.

* Compile collation logic.

* Move back to refs. Yey.

* Remove "object" id for storage access.

* Fix test.

* Fix up rest of tests.

* remove unwrap.

* Expose set/get code in externalities

Also improve tests and add nice wrappers in rust-wasm.

* Add validator set.

* Introduce validator set into externalities and test.

* Add another external function.

* Remove code and validators; use storage for everything.

* Introduce validators function.

* Tests (and a fix) for the validators getter.

* Allow calls into runtime to return data.

* Remove unneeded trace.

* Make runtime printing a bit nicer.

* Create separate runtimes for testing and polkadot.

* Remove commented code.

* Use new path.

* Refactor into shared support module.

* Fix warning.

* Remove unwraps.

* Make macro a little less unhygenic.

* Add wasm files.

substrate/runtime/pwasm-libc/src/lib.rs

@@ -0,0 +1,46 @@
+#![warn(missing_docs)]
+#![cfg_attr(feature = "strict", deny(warnings))]
+#![no_std]
+
+//! libc externs crate
+
+extern "C" {
+	fn ext_memcpy(dest: *mut u8, src: *const u8, n: usize) -> *mut u8;
+	fn ext_memmove(dest: *mut u8, src: *const u8, n: usize) -> *mut u8;
+	fn ext_memset(dest: *mut u8, c: i32, n: usize) -> *mut u8;
+	fn ext_malloc(size: usize) -> *mut u8;
+	fn ext_free(ptr: *mut u8);
+}
+
+// Declaring these function here prevents Emscripten from including it's own verisons
+// into final binary.
+
+/// memcpy extern
+#[no_mangle]
+pub unsafe extern "C" fn memcpy(dest: *mut u8, src: *const u8, n: usize) -> *mut u8 {
+	ext_memcpy(dest, src, n)
+}
+
+/// memmove extern
+#[no_mangle]
+pub unsafe extern "C" fn memmove(dest: *mut u8, src: *const u8, n: usize) -> *mut u8 {
+	ext_memmove(dest, src, n)
+}
+
+/// memset extern
+#[no_mangle]
+pub unsafe extern "C" fn memset(dest: *mut u8, c: i32, n: usize) -> *mut u8 {
+	ext_memset(dest, c, n)
+}
+
+/// malloc extern
+#[no_mangle]
+pub unsafe extern "C" fn malloc(size: usize) -> *mut u8 {
+	ext_malloc(size)
+}
+
+/// free extern
+#[no_mangle]
+pub unsafe extern "C" fn free(ptr: *mut u8) {
+	ext_free(ptr);
+}