Make the clang module container format selectable from the command line.

- introduces a new cc1 option -fmodule-format=[raw,obj]
  with 'raw' being the default
- supports arbitrary module container formats that libclang is agnostic to
- adds the format to the module hash to avoid collisions
- splits the old PCHContainerOperations into PCHContainerWriter and
  a PCHContainerReader.

Thanks to Richard Smith for reviewing this patch!

llvm-svn: 242499

clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp

@@ -156,7 +156,7 @@ public:
 } // namespace
 
 std::unique_ptr<ASTConsumer>
-ObjectFilePCHContainerOperations::CreatePCHContainerGenerator(
+ObjectFilePCHContainerWriter::CreatePCHContainerGenerator(
     DiagnosticsEngine &Diags, const HeaderSearchOptions &HSO,
     const PreprocessorOptions &PPO, const TargetOptions &TO,
     const LangOptions &LO, const std::string &MainFileName,
@@ -166,7 +166,7 @@ ObjectFilePCHContainerOperations::CreatePCHContainerGenerator(
       Diags, HSO, PPO, TO, LO, MainFileName, OutputFileName, OS, Buffer);
 }
 
-void ObjectFilePCHContainerOperations::ExtractPCH(
+void ObjectFilePCHContainerReader::ExtractPCH(
     llvm::MemoryBufferRef Buffer, llvm::BitstreamReader &StreamFile) const {
   if (auto OF = llvm::object::ObjectFile::createObjectFile(Buffer)) {
     auto *Obj = OF.get().get();