Update to cranelift 0.20.0.

The biggest change is the split from FunctionIndex to
DefinedFuncIndex to FuncIndex. Take better advantage of this by
converting several Vecs to PrimaryMaps.

Also, table_addr can now handle indices of the table index type,
so we don't need to explicitly uextend them anymore.

lib/obj/src/emit_module.rs

@@ -1,5 +1,6 @@
 use cranelift_codegen::settings;
 use cranelift_codegen::settings::Configurable;
+use cranelift_entity::EntityRef;
 use faerie::Artifact;
 use wasmtime_environ::{Compilation, Module, Relocations};
 
@@ -12,7 +13,8 @@ pub fn emit_module(
     relocations: &Relocations,
 ) -> Result<(), String> {
     debug_assert!(
-        module.start_func.is_none() || module.start_func.unwrap() >= module.imported_funcs.len(),
+        module.start_func.is_none()
+            || module.start_func.unwrap().index() >= module.imported_funcs.len(),
         "imported start functions not supported yet"
     );
 
@@ -21,11 +23,11 @@ pub fn emit_module(
         .enable("enable_verifier")
         .expect("Missing enable_verifier setting");
 
-    for (i, function_relocs) in relocations.iter().enumerate() {
+    for (i, function_relocs) in relocations.iter() {
         assert!(function_relocs.is_empty(), "relocations not supported yet");
         let body = &compilation.functions[i];
-        let func_index = module.imported_funcs.len() + i;
-        let string_name = format!("wasm_function[{}]", func_index);
+        let func_index = module.func_index(i);
+        let string_name = format!("wasm_function[{}]", func_index.index());
 
         obj.define(string_name, body.clone())
             .map_err(|err| format!("{}", err))?;

lib/obj/src/lib.rs

@@ -13,6 +13,7 @@
 )]
 
 extern crate cranelift_codegen;
+extern crate cranelift_entity;
 extern crate faerie;
 extern crate wasmtime_environ;