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/AST/RawCommentList.cpp b/clang/lib/AST/RawCommentList.cpp
index 1f504fb..ab873a3 100644
--- a/clang/lib/AST/RawCommentList.cpp
+++ b/clang/lib/AST/RawCommentList.cpp
@@ -415,7 +415,7 @@
       Str.pop_back();
   };
 
-  // Proces first line separately to remember indent for the following lines.
+  // Process first line separately to remember indent for the following lines.
   if (!LexLine(/*IsFirstLine=*/true)) {
     DropTrailingNewLines(Result);
     return Result;