Delay creating an alias for @@@.

With this we only create an alias for @@@ once we know if it should
use @ or @@. This avoids last minutes renames and hacks to handle MS
names.

This only handles the ELF writer. LTO still has issues with @@@
aliases.

llvm-svn: 327160
diff --git a/llvm/lib/Object/RecordStreamer.h b/llvm/lib/Object/RecordStreamer.h
index 4d11909..e1e23f2 100644
--- a/llvm/lib/Object/RecordStreamer.h
+++ b/llvm/lib/Object/RecordStreamer.h
@@ -54,7 +54,7 @@
   void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                         unsigned ByteAlignment) override;
   /// Record .symver aliases for later processing.
-  void emitELFSymverDirective(MCSymbol *Alias,
+  void emitELFSymverDirective(StringRef AliasName,
                               const MCSymbol *Aliasee) override;
   /// Return the map of .symver aliasee to associated aliases.
   DenseMap<const MCSymbol *, std::vector<MCSymbol *>> &symverAliases() {