Install notion of diagnostic handler into PNaCl bitcode readers.

lib/Bitcode/NaCl/TestUtils/NaClBitcodeTextReader.cpp

 //===- NaClBitcodeTextReader.cpp - Read texual bitcode record list --------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // Implements bitcode reader from textual form.
@@ skipping 269 matching lines @@
   SmallVector<char, 1024> Buffer;
 
   // Fill Buffer with corresponding bitcode records from Filename.
   if (std::error_code EC =
       readNaClRecordTextAndBuildBitcode(Filename, Buffer, Verbose))
     return EC;
 
   // Parse buffer as ordinary binary bitcode file.
   StringRef BitcodeBuffer(Buffer.data(),  Buffer.size());
   MemoryBufferRef MemBufRef(BitcodeBuffer, Filename);
-  return NaClParseBitcodeFile(MemBufRef, Context, Verbose);
+  DiagnosticHandlerFunction DiagnosticHandler = nullptr;
+  return NaClParseBitcodeFile(MemBufRef, Context, DiagnosticHandler, Verbose);
 }