Fix typo

llvm-svn: 342361
diff --git a/libcxx/include/__threading_support b/libcxx/include/__threading_support
index 3c1eff2..2024900 100644
--- a/libcxx/include/__threading_support
+++ b/libcxx/include/__threading_support
@@ -70,7 +70,7 @@
 
 typedef pthread_t __libcpp_thread_t;
 
-// Thrad Local Storage
+// Thread Local Storage
 typedef pthread_key_t __libcpp_tls_key;
 
 #define _LIBCPP_TLS_DESTRUCTOR_CC