Fix covered-switch warning.

llvm-svn: 220456
diff --git a/clang/lib/Lex/ModuleMap.cpp b/clang/lib/Lex/ModuleMap.cpp
index f5fc111..865b62a 100644
--- a/clang/lib/Lex/ModuleMap.cpp
+++ b/clang/lib/Lex/ModuleMap.cpp
@@ -2305,6 +2305,7 @@
     case MMToken::RequiresKeyword:
     case MMToken::Star:
     case MMToken::StringLiteral:
+    case MMToken::TextualKeyword:
     case MMToken::UmbrellaKeyword:
     case MMToken::UseKeyword:
       Diags.Report(Tok.getLocation(), diag::err_mmap_expected_module);