Clang side changes for fixing load order problems with PassRegistry

[zturner]

Summary

(As with the other change, I don't know who the correct reviewer is. Please re-assign if I've chosen incorrectly).

See http://reviews.llvm.org/D3996 for a more comprehensive description of this change.

This patch simply instantiates the PassRegistry in main for clang.

tools/driver/cc1_main.cpp

int cc1_main(const char **ArgBegin, const char **ArgEnd,
 
   // Initialize targets first, so that --version shows registered targets.
   llvm::InitializeAllTargets();
   llvm::InitializeAllTargetMCs();
   llvm::InitializeAllAsmPrinters();
   llvm::InitializeAllAsmParsers();
 
 #ifdef LINK_POLLY_INTO_TOOLS
+  PassRegistry::initializePassRegistry();
   llvm::PassRegistry &Registry = *llvm::PassRegistry::getPassRegistry();
   polly::initializePollyPasses(Registry);
 #endif
 
   // Buffer diagnostics from argument parsing so that we can output them using a
   // well formed diagnostic object.
   IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts = new DiagnosticOptions();
   TextDiagnosticBuffer *DiagsBuffer = new TextDiagnosticBuffer;

tools/driver/driver.cpp

 #include "clang/Basic/DiagnosticOptions.h"
 #include "clang/Driver/Compilation.h"
 #include "clang/Driver/Driver.h"
 #include "clang/Driver/DriverDiagnostic.h"
 #include "clang/Driver/Options.h"
 #include "clang/Frontend/CompilerInvocation.h"
 #include "clang/Frontend/TextDiagnosticPrinter.h"
 #include "clang/Frontend/Utils.h"
+#include "llvm/PassRegistry.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/Config/config.h"
 #include "llvm/Option/ArgList.h"
 #include "llvm/Option/OptTable.h"
 #include "llvm/Option/Option.h"
if (EC) {
     llvm::errs() << "error: couldn't get arguments: " << EC.message() << '\n';
     return 1;
   }
 
   std::set<std::string> SavedStrings;
   StringSetSaver Saver(SavedStrings);
   llvm::cl::ExpandResponseFiles(Saver, llvm::cl::TokenizeGNUCommandLine, argv);
 
+  llvm::PassRegistry::initializePassRegistry();
+
   // Handle -cc1 integrated tools.
   if (argv.size() > 1 && StringRef(argv[1]).startswith("-cc1")) {
     StringRef Tool = argv[1] + 4;
 
     if (Tool == "")
       return cc1_main(argv.data()+2, argv.data()+argv.size(), argv[0],
                       (void*) (intptr_t) GetExecutablePath);
     if (Tool == "as")