misc: Remove unnecessary "extern crate"

Now all crates use edition = "2018" then the majority of the "extern
crate" statements can be removed. Only those for importing macros need
to remain.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

virtio-devices/src/balloon.rs

@@ -17,7 +17,6 @@ use super::{
     VirtioCommon, VirtioDevice, VirtioDeviceType, EPOLL_HELPER_EVENT_LAST, VIRTIO_F_VERSION_1,
 };
 use crate::seccomp_filters::{get_seccomp_filter, Thread};
-use crate::vm_memory::GuestMemory;
 use crate::{VirtioInterrupt, VirtioInterruptType};
 use libc::EFD_NONBLOCK;
 use seccomp::{SeccompAction, SeccompFilter};
@@ -29,6 +28,7 @@ use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
 use std::sync::mpsc;
 use std::sync::{Arc, Barrier, Mutex};
 use std::thread;
+use vm_memory::GuestMemory;
 use vm_memory::{
     Address, ByteValued, Bytes, GuestAddress, GuestAddressSpace, GuestMemoryAtomic,
     GuestMemoryError, GuestMemoryMmap,

virtio-devices/src/lib.rs

@@ -10,21 +10,12 @@
 
 //! Implements virtio devices, queues, and transport mechanisms.
 
-extern crate arc_swap;
-extern crate epoll;
 #[macro_use]
 extern crate event_monitor;
 #[macro_use]
 extern crate log;
-extern crate pci;
-extern crate serde;
 #[macro_use]
 extern crate serde_derive;
-extern crate serde_json;
-extern crate vhost;
-extern crate virtio_bindings;
-extern crate vm_device;
-extern crate vm_memory;
 
 use std::convert::TryInto;
 use std::io;

virtio-devices/src/transport/pci_common_config.rs

@@ -5,7 +5,6 @@
 // Copyright © 2019 Intel Corporation
 //
 // SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause
-extern crate byteorder;
 
 use crate::{Queue, VirtioDevice};
 use byteorder::{ByteOrder, LittleEndian};

virtio-devices/src/transport/pci_device.rs

@@ -6,11 +6,6 @@
 //
 // SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause
 
-extern crate pci;
-extern crate vm_allocator;
-extern crate vm_memory;
-extern crate vmm_sys_util;
-
 use super::VirtioPciCommonConfig;
 use crate::transport::VirtioTransport;
 use crate::{

virtio-devices/src/vhost_user/mod.rs

@@ -1,12 +1,6 @@
 // Copyright 2019 Intel Corporation. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0
 
-extern crate epoll;
-extern crate net_util;
-extern crate vhost;
-extern crate virtio_bindings;
-extern crate vm_memory;
-
 use std::io;
 use vhost::Error as VhostError;
 use vm_memory::Error as MmapError;