Allow aliases to be unnamed_addr.

Alias with unnamed_addr were in a strange state. It is stored in GlobalValue,
the language reference talks about "unnamed_addr aliases" but the verifier
was rejecting them.

It seems natural to allow unnamed_addr in aliases:

* It is a property of how it is accessed, not of the data itself.
* It is perfectly possible to write code that depends on the address
of an alias.

This patch then makes unname_addr legal for aliases. One side effect is that
the syntax changes for a corner case: In globals, unnamed_addr is now printed
before the address space.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210302 91177308-0d34-0410-b5e6-96231b3b80d8

lib/IR/Verifier.cpp

@@ -517,7 +517,6 @@ void Verifier::visitGlobalAlias(const GlobalAlias &GA) {
   Assert1(Aliasee, "Aliasee cannot be NULL!", &GA);
   Assert1(GA.getType() == Aliasee->getType(),
           "Alias and aliasee types should match!", &GA);
-  Assert1(!GA.hasUnnamedAddr(), "Alias cannot have unnamed_addr!", &GA);
 
   Assert1(isa<GlobalValue>(Aliasee) || isa<ConstantExpr>(Aliasee),
           "Aliasee should be either GlobalValue or ConstantExpr", &GA);