Frontend: replicate clang SVN r285660

The block info block does not require an explicit abbreviation width as the
local abbreviations are internal to the block.  Remove the parameter similar to
the clang change.

lib/Frontend/SerializedDiagnosticConsumer.cpp

@@ -341,7 +341,7 @@ static void addRangeLocationAbbrev(llvm::BitCodeAbbrev *Abbrev) {
 }
 
 void SerializedDiagnosticConsumer::emitBlockInfoBlock() {
-  State->Stream.EnterBlockInfoBlock(3);
+  State->Stream.EnterBlockInfoBlock();
 
   using namespace llvm;
   llvm::BitstreamWriter &Stream = State->Stream;