Event Loop 2.0 API and Windows implementation (#638)

* Rename EventsLoop and associated types to EventLoop

* Rename WindowEvent::Refresh to WindowEvent::Redraw

* Remove second thread from win32 backend

* Update run_forever to hijack thread

* Replace windows Mutex with parking_lot Mutex

* Implement new ControlFlow and associated events

* Add StartCause::Init support, timer example

* Add ability to send custom user events

* Fully invert windows control flow so win32 calls into winit's callback

* Add request_redraw

* Rename platform to platform_impl

* Rename os to platform, add Ext trait postfixes

* Add platform::desktop module with EventLoopExt::run_return

* Re-organize into module structure

* Improve documentation

* Small changes to examples

* Improve docs for run and run_return

* Change instances of "events_loop" to "event_loop"

* Rename MonitorId to MonitorHandle

* Add CHANGELOG entry

* Improve WaitUntil timer precision

* When SendEvent is called during event closure, buffer events

* Fix resize lag when waiting in some situations

* Update send test and errors that broke some examples/APIs

* Improve clarity/fix typos in docs

* Fix unreachable panic after setting ControlFlow to Poll during some RedrawRequested events.

* Fix crash when running in release mode

* Remove crossbeam dependency and make drop events work again

* Remove serde implementations from ControlFlow

* Fix 1.24.1 build

* Fix freeze when setting decorations

* Replace &EventLoop in callback with &EventLoopWindowTarget

* Document and implement Debug for EventLoopWindowTarget

* Fix some deadlocks that could occur when changing window state

* Fix thread executor not executing closure when called from non-loop thread

* Fix buffered events not getting dispatched

* Fix crash with runner refcell not getting dropped

* Address review feedback

* Fix CHANGELOG typo

* Catch panics in user callback

src/platform_impl/android/ffi.rs

@@ -0,0 +1,108 @@
+#![allow(dead_code)]
+#![allow(non_snake_case)]
+#![allow(non_camel_case_types)]
+#![allow(non_upper_case_globals)]
+
+use libc;
+use std::os::raw;
+
+#[link(name = "android")]
+#[link(name = "EGL")]
+#[link(name = "GLESv2")]
+extern {}
+
+/**
+ * asset_manager.h
+ */
+pub type AAssetManager = raw::c_void;
+
+/**
+ * native_window.h
+ */
+pub type ANativeWindow = raw::c_void;
+
+extern {
+    pub fn ANativeWindow_getHeight(window: *const ANativeWindow) -> libc::int32_t;
+    pub fn ANativeWindow_getWidth(window: *const ANativeWindow) -> libc::int32_t;
+}
+
+/**
+ * native_activity.h
+ */
+pub type JavaVM = ();
+pub type JNIEnv = ();
+pub type jobject = *const libc::c_void;
+
+pub type AInputQueue = ();  // FIXME: wrong
+pub type ARect = ();  // FIXME: wrong
+
+#[repr(C)]
+pub struct ANativeActivity {
+    pub callbacks: *mut ANativeActivityCallbacks,
+    pub vm: *mut JavaVM,
+    pub env: *mut JNIEnv,
+    pub clazz: jobject,
+    pub internalDataPath: *const libc::c_char,
+    pub externalDataPath: *const libc::c_char,
+    pub sdkVersion: libc::int32_t,
+    pub instance: *mut libc::c_void,
+    pub assetManager: *mut AAssetManager,
+    pub obbPath: *const libc::c_char,
+}
+
+#[repr(C)]
+pub struct ANativeActivityCallbacks {
+    pub onStart: extern fn(*mut ANativeActivity),
+    pub onResume: extern fn(*mut ANativeActivity),
+    pub onSaveInstanceState: extern fn(*mut ANativeActivity, *mut libc::size_t),
+    pub onPause: extern fn(*mut ANativeActivity),
+    pub onStop: extern fn(*mut ANativeActivity),
+    pub onDestroy: extern fn(*mut ANativeActivity),
+    pub onWindowFocusChanged: extern fn(*mut ANativeActivity, libc::c_int),
+    pub onNativeWindowCreated: extern fn(*mut ANativeActivity, *const ANativeWindow),
+    pub onNativeWindowResized: extern fn(*mut ANativeActivity, *const ANativeWindow),
+    pub onNativeWindowRedrawNeeded: extern fn(*mut ANativeActivity, *const ANativeWindow),
+    pub onNativeWindowDestroyed: extern fn(*mut ANativeActivity, *const ANativeWindow),
+    pub onInputQueueCreated: extern fn(*mut ANativeActivity, *mut AInputQueue),
+    pub onInputQueueDestroyed: extern fn(*mut ANativeActivity, *mut AInputQueue),
+    pub onContentRectChanged: extern fn(*mut ANativeActivity, *const ARect),
+    pub onConfigurationChanged: extern fn(*mut ANativeActivity),
+    pub onLowMemory: extern fn(*mut ANativeActivity),
+}
+
+/**
+ * looper.h
+ */
+pub type ALooper = ();
+
+#[link(name = "android")]
+extern {
+    pub fn ALooper_forThread() -> *const ALooper;
+    pub fn ALooper_acquire(looper: *const ALooper);
+    pub fn ALooper_release(looper: *const ALooper);
+    pub fn ALooper_prepare(opts: libc::c_int) -> *const ALooper;
+    pub fn ALooper_pollOnce(timeoutMillis: libc::c_int, outFd: *mut libc::c_int,
+        outEvents: *mut libc::c_int, outData: *mut *mut libc::c_void) -> libc::c_int;
+    pub fn ALooper_pollAll(timeoutMillis: libc::c_int, outFd: *mut libc::c_int,
+        outEvents: *mut libc::c_int, outData: *mut *mut libc::c_void) -> libc::c_int;
+    pub fn ALooper_wake(looper: *const ALooper);
+    pub fn ALooper_addFd(looper: *const ALooper, fd: libc::c_int, ident: libc::c_int,
+        events: libc::c_int, callback: ALooper_callbackFunc, data: *mut libc::c_void)
+        -> libc::c_int;
+    pub fn ALooper_removeFd(looper: *const ALooper, fd: libc::c_int) -> libc::c_int;
+}
+
+pub const ALOOPER_PREPARE_ALLOW_NON_CALLBACKS: libc::c_int = 1 << 0;
+
+pub const ALOOPER_POLL_WAKE: libc::c_int = -1;
+pub const ALOOPER_POLL_CALLBACK: libc::c_int = -2;
+pub const ALOOPER_POLL_TIMEOUT: libc::c_int = -3;
+pub const ALOOPER_POLL_ERROR: libc::c_int = -4;
+
+pub const ALOOPER_EVENT_INPUT: libc::c_int = 1 << 0;
+pub const ALOOPER_EVENT_OUTPUT: libc::c_int = 1 << 1;
+pub const ALOOPER_EVENT_ERROR: libc::c_int = 1 << 2;
+pub const ALOOPER_EVENT_HANGUP: libc::c_int = 1 << 3;
+pub const ALOOPER_EVENT_INVALID: libc::c_int = 1 << 4;
+
+pub type ALooper_callbackFunc = extern fn(libc::c_int, libc::c_int, *mut libc::c_void) -> libc::c_int;