add some comments.

llvm-svn: 43079

clang/include/clang/Lex/Lexer.h

@@ -139,6 +139,8 @@ public:
     LexingRawMode = true;
     Lex(Result);
     LexingRawMode = false;
+    // Note that lexing to the end of the buffer doesn't implicitly delete the
+    // lexer when in raw mode.
     return BufferPtr == BufferEnd; 
   }
   

clang/include/clang/Lex/Preprocessor.h

@@ -33,7 +33,7 @@ class TargetInfo;
 class PPCallbacks;
 class DirectoryLookup;
 
-/// Preprocessor - This object forms engages in a tight little dance to
+/// Preprocessor - This object engages in a tight little dance with the lexer to
 /// efficiently preprocess tokens.  Lexers know only about tokens within a
 /// single source file, and don't know anything about preprocessor-level issues
 /// like the #include stack, token expansion, etc.