Make UsingShadowDecls redeclarable. This fixes some visibility problems with
modules.

With this fixed, I no longer see any test regressions in the libc++ test suite
when enabling a single-module module.map for libc++ (other than issues with my
system headers).


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@193219 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Serialization/ASTCommon.cpp b/lib/Serialization/ASTCommon.cpp
index 79bba0c..a817687 100644
--- a/lib/Serialization/ASTCommon.cpp
+++ b/lib/Serialization/ASTCommon.cpp
@@ -165,6 +165,7 @@
   case Decl::CXXConstructor:
   case Decl::CXXDestructor:
   case Decl::CXXConversion:
+  case Decl::UsingShadow:
   case Decl::Var:
   case Decl::FunctionTemplate:
   case Decl::ClassTemplate:
@@ -192,7 +193,6 @@
   case Decl::NonTypeTemplateParm:
   case Decl::TemplateTemplateParm:
   case Decl::Using:
-  case Decl::UsingShadow:
   case Decl::ObjCMethod:
   case Decl::ObjCCategory:
   case Decl::ObjCCategoryImpl: