Misc typos fixes in ./lib folder

Summary: Found via `codespell -q 3 -I ../clang-whitelist.txt -L uint,importd,crasher,gonna,cant,ue,ons,orign,ned`

Reviewers: teemperor

Reviewed By: teemperor

Subscribers: teemperor, jholewinski, jvesely, nhaehnle, whisperity, jfb, cfe-commits

Differential Revision: https://reviews.llvm.org/D55475

llvm-svn: 348755
diff --git a/clang/lib/CodeGen/CGBlocks.cpp b/clang/lib/CodeGen/CGBlocks.cpp
index db81734..6631bfb 100644
--- a/clang/lib/CodeGen/CGBlocks.cpp
+++ b/clang/lib/CodeGen/CGBlocks.cpp
@@ -175,7 +175,7 @@
 ///   unsigned long reserved;
 ///   unsigned long size;  // size of Block_literal metadata in bytes.
 ///   void *copy_func_helper_decl;  // optional copy helper.
-///   void *destroy_func_decl; // optioanl destructor helper.
+///   void *destroy_func_decl; // optional destructor helper.
 ///   void *block_method_encoding_address; // @encode for block literal signature.
 ///   void *block_layout_info; // encoding of captured block variables.
 /// };