THRIFT-2849: spelling errors fixed using codespell tool

Client: All
Patch: Anatol Pomozov

This closes #281
diff --git a/lib/d/src/thrift/async/libevent.d b/lib/d/src/thrift/async/libevent.d
index 3358bef..967c41f 100644
--- a/lib/d/src/thrift/async/libevent.d
+++ b/lib/d/src/thrift/async/libevent.d
@@ -430,7 +430,7 @@
   Work[][TAsyncTransport] workQueues_;
 
   /// The total number of work items not yet finished (queued and currently
-  /// excecuted) and delays not yet executed.
+  /// executed) and delays not yet executed.
   uint queuedCount_;
 
   /// Protects queuedCount_.