[modules ts] Basic for module linkage.

In addition to the formal linkage rules, the Modules TS includes cases where
internal-linkage symbols within a module interface unit can be referenced from
outside the module via exported inline functions / templates. We give such
declarations "module-internal linkage", which is formally internal linkage, but
results in an externally-visible symbol.

llvm-svn: 307434
diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index e6d38af..c82b967 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -2959,6 +2959,8 @@
     return llvm::GlobalValue::InternalLinkage;
 
   case VisibleNoLinkage:
+  case ModuleInternalLinkage:
+  case ModuleLinkage:
   case ExternalLinkage:
     // RTTI is not enabled, which means that this type info struct is going
     // to be used for exception handling. Give it linkonce_odr linkage.