Add a SymbolicFile interface between Binary and ObjectFile.

This interface allows IRObjectFile to be implemented without having dummy
methods for all section and segment related methods.

Both llvm-ar and llvm-nm are changed to use it. Unfortunately the mangler is
still not plugged in since it requires some refactoring to make a Module hold
a DataLayout.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201881 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Object/ObjectFile.cpp

@@ -25,7 +25,16 @@ void ObjectFile::anchor() { }
 
 ObjectFile::ObjectFile(unsigned int Type, MemoryBuffer *Source,
                        bool BufferOwned)
-    : Binary(Type, Source, BufferOwned) {}
+    : SymbolicFile(Type, Source, BufferOwned) {}
+
+error_code ObjectFile::printSymbolName(raw_ostream &OS,
+                                       DataRefImpl Symb) const {
+  StringRef Name;
+  if (error_code EC = getSymbolName(Symb, Name))
+    return EC;
+  OS << Name;
+  return object_error::success;
+}
 
 error_code ObjectFile::getSymbolAlignment(DataRefImpl DRI,
                                           uint32_t &Result) const {