Add clang-format config file

This is used in preparation to enable automatic code-formatting in the
following commits.  For now let's just add a clang-format config file,
formatting of source files will follow.

related: #16019

Signed-off-by: Luca Saccarola <github.e41mv@aleeas.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/Filelist b/Filelist
index 1f899b5..f65504e 100644
--- a/Filelist
+++ b/Filelist
@@ -17,6 +17,7 @@
 		.gitignore \
 		.hgignore \
 		.appveyor.yml \
+		.clang-format \
 		.codecov.yml \
 		.editorconfig \
 		ci/appveyor.bat \