Initial reorg.

This is largely the same as #305, but updated for the current tree.

crates/wasi-common/wig/Cargo.toml

@@ -0,0 +1,20 @@
+[package]
+name = "wig"
+version = "0.1.0"
+authors = ["Dan Gohman <sunfish@mozilla.com>"]
+edition = "2018"
+categories = ["wasm"]
+keywords = ["webassembly", "wasm"]
+license = "Apache-2.0 WITH LLVM-exception"
+repository = "https://github.com/CraneStation/wasmtime"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+quote = "1.0.2"
+proc-macro2 = "1.0.6"
+# We include the WASI repo primarily for the witx files, but it's also useful
+# to use the witx parser it contains, rather than the witx crate from
+# crates.io, so that it always matches the version of the witx files.
+witx = { path = "../WASI/tools/witx" }