Spelling fixes (#571)

* docs: fix spelling and whitespace errors

tokio-threadpool/src/worker/mod.rs

@@ -732,7 +732,7 @@ impl Worker {
                     }
                 }
                 Shutdown | Running => {
-                    // To get here, the block above transitioned the tate to
+                    // To get here, the block above transitioned the state to
                     // `Sleeping`. No other thread can concurrently
                     // transition to `Shutdown` or `Running`.
                     unreachable!();
@@ -805,7 +805,7 @@ impl Worker {
                         }
                     }
                     Shutdown | Running => {
-                        // To get here, the block above transitioned the tate to
+                        // To get here, the block above transitioned the state to
                         // `Sleeping`. No other thread can concurrently
                         // transition to `Shutdown` or `Running`.
                         unreachable!();

tokio-threadpool/src/worker/stack.rs

@@ -46,7 +46,7 @@ pub(crate) const EMPTY: usize = MAX_WORKERS;
 /// Used to mark the stack as terminated
 pub(crate) const TERMINATED: usize = EMPTY + 1;
 
-/// How many bits the treiber ABA guard is offset by
+/// How many bits the Treiber ABA guard is offset by
 const ABA_GUARD_SHIFT: usize = 16;
 
 #[cfg(target_pointer_width = "64")]
@@ -215,7 +215,7 @@ impl State {
 
     #[inline]
     fn set_head(&mut self, val: usize) {
-        // The ABA guard protects against the ABA problem w/ treiber stacks
+        // The ABA guard protects against the ABA problem w/ Treiber stacks
         let aba_guard = ((self.0 >> ABA_GUARD_SHIFT) + 1) & ABA_GUARD_MASK;
 
         self.0 = (aba_guard << ABA_GUARD_SHIFT) | val;