implement the microsoft/gnu "__COUNTER__" macro: rdar://4329310


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@68933 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Lex/Preprocessor.cpp b/lib/Lex/Preprocessor.cpp
index 097b454..2c9b0b9 100644
--- a/lib/Lex/Preprocessor.cpp
+++ b/lib/Lex/Preprocessor.cpp
@@ -53,7 +53,8 @@
     SourceMgr(SM), HeaderInfo(Headers), Identifiers(opts, IILookup),
     CurPPLexer(0), CurDirLookup(0), Callbacks(0) {
   ScratchBuf = new ScratchBuffer(SourceMgr);
-
+  CounterValue = 0; // __COUNTER__ starts at 0.
+      
   // Clear stats.
   NumDirectives = NumDefined = NumUndefined = NumPragma = 0;
   NumIf = NumElse = NumEndif = 0;