message: fix(clif-backend) Remove unused imports.
  This patch removes unused imports reported by `rustc` as warnings.
diff: @@ -18,11 +18,7 @@ use nix::sys::signal::{
  use std::cell::{Cell, UnsafeCell};
  use std::ptr;
  use std::sync::Once;
  -use wasmer_runtime_core::{
  - error::{RuntimeError, RuntimeResult},
  - structures::TypedIndex,
  - types::{MemoryIndex, TableIndex},
  -};
  +use wasmer_runtime_core::error::{RuntimeError, RuntimeResult};
  extern "C" fn signal_trap_handler(
  signum: ::nix::libc::c_int,
  