Fixed some typos, courtesy of codespell

Main change is the conversion from the British cancelling/-ed to the
American canceling/-ed.

src/libstrongswan/threading/thread.c

@@ -84,7 +84,7 @@ struct private_thread_t {
 	bool detached_or_joined;
 
 	/**
-	 * TRUE if the threads has terminated (cancelled, via thread_exit or
+	 * TRUE if the threads has terminated (canceled, via thread_exit or
 	 * returned from the main function)
 	 */
 	bool terminated;
@@ -130,7 +130,7 @@ static thread_value_t *current_thread;
 #endif
 
 /* the signal handler for SIG_CANCEL uses pthread_exit to terminate the
- * "cancelled" thread */
+ * "canceled" thread */
 static void cancel_signal_handler(int sig)
 {
 	pthread_exit(NULL);

src/libstrongswan/threading/thread.h

@@ -109,7 +109,7 @@ u_int thread_current_id();
 
 /**
  * Push a function onto the current thread's cleanup handler stack.
- * The callback function is called whenever the thread is cancelled, exits or
+ * The callback function is called whenever the thread is canceled, exits or
  * thread_cleanup_pop is called with TRUE as execute argument.
  *
  * @param cleanup		function called on thread exit

src/libstrongswan/threading/windows/thread.c

@@ -87,7 +87,7 @@ struct private_thread_t {
 	bool cancelability;
 
 	/**
-	 * Has the thread been cancelled by thread->cancel()?
+	 * Has the thread been canceled by thread->cancel()?
 	 */
 	bool canceled;