[meta] Make Instruction name/doc Strings so they can be automatically generated;

cranelift/codegen/meta/src/gen_legalizer.rs

@@ -241,7 +241,7 @@ fn emit_runtime_typecheck<'a, 'b>(
 /// Determine if `node` represents one of the value splitting instructions: `isplit` or `vsplit.
 /// These instructions are lowered specially by the `legalize::split` module.
 fn is_value_split(def: &Def) -> bool {
-    let name = def.apply.inst.name;
+    let name = &def.apply.inst.name;
     name == "isplit" || name == "vsplit"
 }