Fix filename in file header comment.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@208380 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Lex/MacroArgs.cpp

@@ -1,4 +1,4 @@
-//===--- TokenLexer.cpp - Lex from a token stream -------------------------===//
+//===--- MacroArgs.cpp - Formal argument info for Macros ------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //