Object, support both mach-o archive t.o.c file names

For historical reasons archives on mach-o have two possible names for the 
file containing the table of contents for the archive: "__.SYMDEF SORTED" 
and "__.SYMDEF".  But the libObject archive reader only supported the former.

This patch fixes llvm::object::Archive to support both names.

llvm-svn: 221747
diff --git a/llvm/lib/Object/Archive.cpp b/llvm/lib/Object/Archive.cpp
index 070fe81..d169dbe 100644
--- a/llvm/lib/Object/Archive.cpp
+++ b/llvm/lib/Object/Archive.cpp
@@ -240,7 +240,7 @@
     if (ec)
       return;
     Name = NameOrErr.get();
-    if (Name == "__.SYMDEF SORTED") {
+    if (Name == "__.SYMDEF SORTED" || Name == "__.SYMDEF") {
       SymbolTable = i;
       ++i;
     }