Rename 'cton_*' library names to match the 'cretonne_*' crate names.

This renames `cton_frontend` to `cretonne_frontend` and so on.

This fixes the first part of #287.

lib/wasm/src/func_translator.rs

@@ -9,7 +9,7 @@ use cretonne::entity::EntityRef;
 use cretonne::ir::{self, Ebb, InstBuilder};
 use cretonne::result::{CtonError, CtonResult};
 use cretonne::timing;
-use cton_frontend::{FunctionBuilder, FunctionBuilderContext, Variable};
+use cretonne_frontend::{FunctionBuilder, FunctionBuilderContext, Variable};
 use environ::FuncEnvironment;
 use state::TranslationState;
 use wasmparser::{self, BinaryReader};