[clang-format] Releasenotes for rL319024 : Add option to group multiple #include blocks when sorting includes

Summary:
This change adds missing releasenotes for commit rL319024
https://reviews.llvm.org/rL319024

Patch by Krzysztof Kapusta

Reviewers: sylvestre.ledru

Reviewed By: sylvestre.ledru

Differential Revision: https://reviews.llvm.org/D40827

llvm-svn: 319748
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 71e330b..8b562bb 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -248,6 +248,19 @@
 * Option -verbose added to the command line.
   Shows the list of processed files.
 
+* Option *IncludeBlocks* added to merge and regroup multiple ``#include`` blocks during sorting.
+
+  +-------------------------+-------------------------+-------------------------+
+  | Before (Preserve)       | Merge                   | Regroup                 |
+  +=========================+=========================+=========================+
+  |  .. code-block:: c++    | .. code-block:: c++     | .. code-block:: c++     |
+  |                         |                         |                         |
+  |   #include "b.h"        |   #include "a.h"        |   #include "a.h"        |
+  |                         |   #include "b.h"        |   #include "b.h"        |
+  |   #include "a.b"        |   #include <lib/main.h> |                         |
+  |   #include <lib/main.h> |                         |   #include <lib/main.h> |
+  +-------------------------+-------------------------+-------------------------+
+
 libclang
 --------