Add a hasExternalLinkage helper. No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176607 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/Sema.cpp b/lib/Sema/Sema.cpp
index 8c79d82..6239172 100644
--- a/lib/Sema/Sema.cpp
+++ b/lib/Sema/Sema.cpp
@@ -360,7 +360,7 @@
       return !SemaRef->ShouldWarnIfUnusedFileScopedDecl(DeclToCheck);
   }
 
-  if (D->getLinkage() == ExternalLinkage)
+  if (D->hasExternalLinkage())
     return true;
 
   return false;
@@ -402,13 +402,13 @@
     if (FunctionDecl *FD = dyn_cast<FunctionDecl>(ND)) {
       if (FD->isDefined())
         continue;
-      if (FD->getLinkage() == ExternalLinkage &&
+      if (FD->hasExternalLinkage() &&
           !FD->getMostRecentDecl()->isInlined())
         continue;
     } else {
       if (cast<VarDecl>(ND)->hasDefinition() != VarDecl::DeclarationOnly)
         continue;
-      if (ND->getLinkage() == ExternalLinkage)
+      if (ND->hasExternalLinkage())
         continue;
     }