Cleanup handling of UniqueExternalLinkage.

This patch renames getLinkage to getLinkageInternal. Only code that
needs to handle UniqueExternalLinkage specially should call this.

Linkage, as defined in the c++ standard, is provided by
getFormalLinkage. It maps UniqueExternalLinkage to ExternalLinkage.

Most places in the compiler actually want isExternallyVisible, which
handles UniqueExternalLinkage as internal.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@181677 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/libclang/CIndex.cpp b/tools/libclang/CIndex.cpp
index c25e625..71827f8 100644
--- a/tools/libclang/CIndex.cpp
+++ b/tools/libclang/CIndex.cpp
@@ -5681,7 +5681,7 @@
 
   const Decl *D = cxcursor::getCursorDecl(cursor);
   if (const NamedDecl *ND = dyn_cast_or_null<NamedDecl>(D))
-    switch (ND->getLinkage()) {
+    switch (ND->getLinkageInternal()) {
       case NoLinkage: return CXLinkage_NoLinkage;
       case InternalLinkage: return CXLinkage_Internal;
       case UniqueExternalLinkage: return CXLinkage_UniqueExternal;