Remove extern crate statements (#3310)

src/platform_impl/linux/x11/ime/context.rs

@@ -86,7 +86,7 @@ extern "C" fn preedit_draw_callback(
     let chg_range =
         call_data.chg_first as usize..(call_data.chg_first + call_data.chg_length) as usize;
     if chg_range.start > client_data.text.len() || chg_range.end > client_data.text.len() {
-        warn!(
+        log::warn!(
             "invalid chg range: buffer length={}, but chg_first={} chg_lengthg={}",
             client_data.text.len(),
             call_data.chg_first,

src/platform_impl/linux/x11/ime/mod.rs

@@ -10,6 +10,10 @@ use std::sync::{
     Arc,
 };
 
+use log::debug;
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+
 use super::{ffi, util, XConnection, XError};
 
 pub use self::context::ImeContextCreationError;