Print a note to the called macro when diagnosing err_embedded_directive

Fixes PR40713, see there for the motivation for this.

Differential Revision: https://reviews.llvm.org/D58161

llvm-svn: 354009
diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
index 5e97d9f..3950174 100644
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -886,6 +886,8 @@
       case tok::pp___include_macros:
       case tok::pp_pragma:
         Diag(Result, diag::err_embedded_directive) << II->getName();
+        Diag(*ArgMacro, diag::note_macro_expansion_here)
+            << ArgMacro->getIdentifierInfo();
         DiscardUntilEndOfDirective();
         return;
       default: