Update witx to 0.9

See WebAssembly/WASI#395

Author: jedisct1

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "witx-docgen"
-version = "0.1.3"
+version = "0.2.0"
 authors = ["Frank Denis <[email protected]>"]
 edition = "2018"
 keywords = ["webassembly", "wasm", "witx", "doc"]
@@ -12,4 +12,4 @@ description = "CLI tool to generate documentation from a WITX file."
 
 [dependencies]
 clap = "2"
-witx = "0.8.7"
+witx = "0.9.0"