Initial reorg.

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

crates/wasi-c/src/host.rs

@@ -0,0 +1,6 @@
+#![allow(non_camel_case_types, non_snake_case, dead_code)]
+
+include!(concat!(env!("OUT_DIR"), "/wasmtime_ssp.rs"));
+
+pub type char = ::std::os::raw::c_char;
+pub type void = ::std::os::raw::c_void;