Handle relocations that don't point to symbols.

In ELF (as in MachO), not all relocations point to symbols. Represent this
properly by using a symbol_iterator instead of a SymbolRef. Update llvm-readobj
ELF's dumper to handle relocatios without symbols.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@183284 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp
index 01a3fd9..0384b32 100644
--- a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp
+++ b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp
@@ -302,10 +302,9 @@
 
   if (isExtern) {
     // Obtain the symbol name which is referenced in the relocation
-    SymbolRef Symbol;
-    RelI.getSymbol(Symbol);
+    symbol_iterator Symbol = RelI.getSymbol();
     StringRef TargetName;
-    Symbol.getName(TargetName);
+    Symbol->getName(TargetName);
     // First search for the symbol in the local symbol table
     SymbolTableMap::const_iterator lsi = Symbols.find(TargetName.data());
     if (lsi != Symbols.end()) {