Handle more declarations in DeclContextPrinter to fix -print-decl-contexts crashes

[arphaman]

Summary

This patch handles more declarations in DeclContextPrinter to avoid crashes when clang is given the -print-decl-contexts option. I would like to get an opinion on the testing in this patch - the current -print-decl-contexts test doesn't check the output, so this patch follows the same testing protocol. Do you think I should also check the output of -print-decl-contexts?

This patch contains 7 commits that I squashed just for review to make it easier:

• DeclContextPrinter: Handle StaticAssertDecl
• DeclContextPrinter: Handle variable template declaration
• DeclContextPrinter: Handle Access specifier declaration
• DeclContextPrinter: Handle ClassTemplateSpecialization and ClassTemplatePartialSpecialization declarations
• DeclContextPrinter: Handle EmptyDecl
• DeclContextPrinter: Handle UsingDecl
• DeclContextPrinter: Handle FriendDecl

Thanks

[mehdi_amini]

Testing is in line with the existing testing.
It is not great, but at the same time is a development/debugging tool right?

cfe/trunk/lib/Frontend/ASTConsumers.cpp

case Decl::ClassTemplate: {
       ClassTemplateDecl *CTD = cast<ClassTemplateDecl>(I);
       Out << "<class template> " << *CTD << '\n';
       break;
     }
     case Decl::OMPThreadPrivate: {
       Out << "<omp threadprivate> " << '"' << I << "\"\n";
       break;
     }
+    case Decl::Friend: {
+      Out << "<friend>";
+      if (const NamedDecl *ND = cast<FriendDecl>(I)->getFriendDecl())
+        Out << ' ' << *ND;
+      Out << "\n";
+      break;
+    }
     default:
       Out << "DeclKind: " << DK << '"' << I << "\"\n";
       llvm_unreachable("decl unhandled");
     }
   }
 }
 std::unique_ptr<ASTConsumer> clang::CreateDeclContextPrinter() {
   return llvm::make_unique<DeclContextPrinter>();
 }

cfe/trunk/test/Coverage/cxx-language-features.inc

 
 class Derived1 : Base1, virtual public Base2 { };
 
 /* Template classes, template functions */
 enum E1 { EC1 };
 template <E1 v> class C1 {};
 template <E1 v> C1<v> f1() { return C1<v>(); }
 void f2() { f1<EC1>(); }
+
+// Friend declarations
+struct FriendlyStruct {
+  friend bool operator==(FriendlyStruct, FriendlyStruct) { return true; }
+  friend struct FriendedStruct;
+};
+
+struct FriendedStruct { };