Start work on SerializedDiagnosticPrinter, a new DiagnosticConsumer that serializes out the diagnostics for a given translation unit to a bit code file. This is a WIP.

The motivation for this new DiagnosticConsumer is to provide a way for tools invoking the compiler
to get its diagnostics via a libclang interface, rather than textually parsing the compiler output.
This gives us flexibility to change the compiler's textual output, but have a structured data format
for clients to use to get the diagnostics via a stable API.

I have no tests for this, but llvm-bcanalyzer so far shows that the emitted file is well-formed.

More work to follow.

llvm-svn: 143259

clang/lib/Frontend/CompilerInvocation.cpp

@@ -1109,6 +1109,8 @@ static void ParseDiagnosticArgs(DiagnosticOptions &Opts, ArgList &Args,
                                 DiagnosticsEngine &Diags) {
   using namespace cc1options;
   Opts.DiagnosticLogFile = Args.getLastArgValue(OPT_diagnostic_log_file);
+  Opts.DiagnosticSerializationFile =
+    Args.getLastArgValue(OPT_diagnostic_serialized_file);
   Opts.IgnoreWarnings = Args.hasArg(OPT_w);
   Opts.NoRewriteMacros = Args.hasArg(OPT_Wno_rewrite_macros);
   Opts.Pedantic = Args.hasArg(OPT_pedantic);