Vendor dependencies

Let's see how I like this workflow.

vendor/crossterm_winapi/src/semaphore.rs

@@ -0,0 +1,41 @@
+use std::{io, ptr};
+
+use winapi::um::synchapi::{CreateSemaphoreW, ReleaseSemaphore};
+
+use crate::{nonnull_handle_result, result, Handle};
+
+/// A [Windows semaphore](https://docs.microsoft.com/en-us/windows/win32/sync/semaphore-objects).
+#[derive(Clone, Debug)]
+pub struct Semaphore(Handle);
+
+impl Semaphore {
+    /// Construct a new semaphore.
+    ///
+    /// This wraps
+    /// [`CreateSemaphoreW`](https://docs.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-createsemaphorew).
+    pub fn new() -> io::Result<Self> {
+        let handle = nonnull_handle_result(unsafe {
+            CreateSemaphoreW(ptr::null_mut(), 0, 1, ptr::null_mut())
+        })?;
+
+        let handle = unsafe { Handle::from_raw(handle) };
+        Ok(Self(handle))
+    }
+
+    /// Release a permit on the semaphore.
+    ///
+    /// This wraps
+    /// [`ReleaseSemaphore`](https://docs.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-releasesemaphore).
+    pub fn release(&self) -> io::Result<()> {
+        result(unsafe { ReleaseSemaphore(*self.0, 1, ptr::null_mut()) })
+    }
+
+    /// Access the underlying handle to the semaphore.
+    pub fn handle(&self) -> &Handle {
+        &self.0
+    }
+}
+
+unsafe impl Send for Semaphore {}
+
+unsafe impl Sync for Semaphore {}