Update clang module map for new excluded .def file.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@374571 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/module.modulemap b/include/clang/module.modulemap
index 0f9b7bb..2cbe865 100644
--- a/include/clang/module.modulemap
+++ b/include/clang/module.modulemap
@@ -18,6 +18,7 @@
   umbrella "AST"
 
   textual header "AST/BuiltinTypes.def"
+  textual header "AST/CXXRecordDeclDefinitionBits.def"
   textual header "AST/OperationKinds.def"
   textual header "AST/TypeLocNodes.def"