Fix typos found by http://github.com/lyda/misspell-check

llvm-svn: 157885
diff --git a/llvm/lib/Transforms/Scalar/ObjCARC.cpp b/llvm/lib/Transforms/Scalar/ObjCARC.cpp
index 9eb1039..d89996a 100644
--- a/llvm/lib/Transforms/Scalar/ObjCARC.cpp
+++ b/llvm/lib/Transforms/Scalar/ObjCARC.cpp
@@ -812,7 +812,7 @@
   case IC_FusedRetainAutorelease:
   case IC_FusedRetainAutoreleaseRV:
     // These functions don't access any memory visible to the compiler.
-    // Note that this doesn't include objc_retainBlock, becuase it updates
+    // Note that this doesn't include objc_retainBlock, because it updates
     // pointers when it copies block data.
     return NoModRef;
   default: