Set KeepFormFeed to true for GNU style and update the release notes

Author: owenca

clang/docs/ReleaseNotes.rst

@@ -705,7 +705,7 @@ clang-format
   multi-line comments without touching their contents, renames ``false`` to
   ``Never``, and ``true`` to ``Always``.
 - Adds ``RemoveEmptyLinesInUnwrappedLines`` option.
-- Adds ``KeepFormFeed`` option.
+- Adds ``KeepFormFeed`` option and set it to ``true`` for ``GNU`` style.
 
 libclang
 --------

clang/lib/Format/Format.cpp

@@ -1929,6 +1929,7 @@ FormatStyle getGNUStyle() {
   Style.ColumnLimit = 79;
   Style.Cpp11BracedListStyle = false;
   Style.FixNamespaceComments = false;
+  Style.KeepFormFeed = true;
   Style.SpaceBeforeParens = FormatStyle::SBPO_Always;
   return Style;
 }