Remove llvm::(cast|isa) from lib/CodeGen/Address.h to fix build with gcc-4.8.1

[sugak]

Summary

gcc-4.8.1 fails to build clang because of a regression in that version of gcc
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58022). See details about the
generated error in https://llvm.org/bugs/show_bug.cgi?id=26362. To work around
the build error, this diff moves definitions cast(clang::CodeGen::Address) and
isa(clang::CodeGen::Address) from llvm to clang namespace. No build errors
are introduced with this change.

I've tested this with gcc-4.8.1 and gcc-4.9.0 both on master and release_38.

[rsmith]

Yuck. Yeah, LGTM. Do you need someone to commit this for you?

Hans, this should go into 3.8 as well.

[rjmccall]

LGTM, too.

[sugak]

@rsmith: yes, I need someone to commit this.

[rsmith]

Thanks, committed as r259598.

lib/CodeGen/Address.h

public:
   }
   static ConstantAddress castImpl(Address addr) {
     return ConstantAddress(llvm::cast<llvm::Constant>(addr.getPointer()),
                            addr.getAlignment());
   }
 };
 
 }
-}
 
-namespace llvm {
-  // Present a minimal LLVM-like casting interface.
-  template <class U> inline U cast(clang::CodeGen::Address addr) {
-    return U::castImpl(addr);
-  }
-  template <class U> inline bool isa(clang::CodeGen::Address addr) {
-    return U::isaImpl(addr);
-  }
-}
+template <class U> inline U cast(CodeGen::Address addr) {
+template <class U> inline bool isa(CodeGen::Address addr) {
 
-namespace clang {
-  // Make our custom isa and cast available in namespace clang, to mirror
-  // what we do for LLVM's versions in Basic/LLVM.h.
-  using llvm::isa;
-  using llvm::cast;
 }
 
 #endif