Add an ELFSymbolRef type.

This allows user code to say Sym.getSize() instead of having to manually fetch
the object.

llvm-svn: 240708
diff --git a/llvm/lib/Object/SymbolSize.cpp b/llvm/lib/Object/SymbolSize.cpp
index 78d6205..730e54c 100644
--- a/llvm/lib/Object/SymbolSize.cpp
+++ b/llvm/lib/Object/SymbolSize.cpp
@@ -55,8 +55,8 @@
     auto Syms = E->symbols();
     if (Syms.begin() == Syms.end())
       Syms = E->getDynamicSymbolIterators();
-    for (SymbolRef Sym : Syms)
-      Ret.push_back({Sym, E->getSymbolSize(Sym)});
+    for (ELFSymbolRef Sym : Syms)
+      Ret.push_back({Sym, Sym.getSize()});
     return Ret;
   }