Revert "[opaque pointer type] update for LLVM API change"

This was the wrong direction to take anyway (because ultimately the
GlobalValue needed the pointee type again and /it/ used
PointerType::getElementType eventually anyway)... let's go a different way.

This reverts commit r236161.

llvm-svn: 247586

clang/lib/CodeGen/CodeGenModule.cpp

@@ -2772,7 +2772,7 @@ void CodeGenModule::EmitAliasDefinition(GlobalDecl GD) {
 
   // Create the new alias itself, but don't set a name yet.
   auto *GA = llvm::GlobalAlias::create(
-      cast<llvm::PointerType>(Aliasee->getType()),
+      cast<llvm::PointerType>(Aliasee->getType())->getElementType(), 0,
       llvm::Function::ExternalLinkage, "", Aliasee, &getModule());
 
   if (Entry) {