Add RTTI support to the SymbolFile class hierarchy

/// implementations of UserExpression - which will be vended through the

/// appropriate TypeSystem.

class UserExpression : public Expression {

  // LLVM RTTI support

  /// LLVM RTTI support.

  static char ID;

public:

namespace lldb_private {

class SymbolFile : public PluginInterface {

  /// LLVM RTTI support.

  static char ID;

public:

  /// LLVM RTTI support.

  /// \{

  virtual bool isA(const void *ClassID) const { return ClassID == &ID; }

  static bool classof(const SymbolFile *obj) { return obj->isA(&ID); }

  /// \}

  // Symbol file ability bits.

  //

  // Each symbol file can claim to support one or more symbol file abilities.

using namespace lldb_private;

using namespace lldb_private::breakpad;

char SymbolFileBreakpad::ID;

class SymbolFileBreakpad::LineIterator {

public:

  // begin iterator for sections of given type

namespace breakpad {

class SymbolFileBreakpad : public SymbolFile {

  /// LLVM RTTI support.

  static char ID;

public:

  /// LLVM RTTI support.

  /// \{

  bool isA(const void *ClassID) const override {

    return ClassID == &ID || SymbolFile::isA(ClassID);

  }

  static bool classof(const SymbolFile *obj) { return obj->isA(&ID); }

  /// \}

  // Static Functions

  static void Initialize();

  static void Terminate();

using namespace lldb;

using namespace lldb_private;

char SymbolFileDWARF::ID;

// static inline bool

// child_requires_parent_class_union_or_struct_to_be_completed (dw_tag_t tag)

//{