[modules] When diagnosing a missing module import, suggest adding a #include if
the current language doesn't have an import syntax and we can figure out a
suitable file to include.

llvm-svn: 267802
diff --git a/clang/test/Modules/Inputs/suggest-include/useprivate3.h b/clang/test/Modules/Inputs/suggest-include/useprivate3.h
new file mode 100644
index 0000000..5d5d221
--- /dev/null
+++ b/clang/test/Modules/Inputs/suggest-include/useprivate3.h
@@ -0,0 +1 @@
+#include "private3.h"