RawCommentList::addComment: fix the assertion so it actually checks that new comment is after the last one (change Comments[0] to Comments.back()), and handle the case of two consecutive comments, e.g. /** *//* */.  There is already a testcase for that (but it didn't trigger the assert because the assert itself was wrong).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@158882 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/RawCommentList.cpp b/lib/AST/RawCommentList.cpp
index 0651029..1baa9b8 100644
--- a/lib/AST/RawCommentList.cpp
+++ b/lib/AST/RawCommentList.cpp
@@ -159,8 +159,10 @@
   assert((Comments.empty() ||
+          Comments.back().getSourceRange().getEnd() ==
+              RC.getSourceRange().getBegin() ||
-              Comments[0].getSourceRange().getEnd(),
+              Comments.back().getSourceRange().getEnd(),
               RC.getSourceRange().getBegin())) &&
          "comments are not coming in source order");