devices: ioapic: Implement the Snapshottable trait

Signed-off-by: Yi Sun <yi.y.sun@linux.intel.com>

devices/src/lib.rs

@@ -6,6 +6,7 @@
 // found in the LICENSE-BSD-3-Clause file.
 
 //! Emulates virtual and hardware devices.
+extern crate anyhow;
 #[macro_use]
 extern crate bitflags;
 extern crate byteorder;
@@ -15,9 +16,14 @@ extern crate libc;
 extern crate log;
 #[cfg(feature = "acpi")]
 extern crate acpi_tables;
+extern crate serde;
 extern crate vm_device;
 extern crate vm_memory;
+extern crate vm_migration;
 extern crate vmm_sys_util;
+#[macro_use]
+extern crate serde_derive;
+extern crate serde_json;
 
 use std::fs::File;
 use std::io;