[gtkmm] Added a candidate .clang-format file.

[Murray Cumming <murrayc src gnome org>]

commit 66f1468b7548e22dd574f170c5930c9e61724200
Author: Murray Cumming <murrayc murrayc com>
Date:   Thu Feb 11 13:03:16 2016 +0100

    Added a candidate .clang-format file.
    
    Please try it out, like so:
    $ clang-format -i `find . -name "*.cc"`
    and then look at
    $ git diff
    
    This is pretty similar to our current format,
    though it fixes a few things, such as my old //commment instead of
    // comment habit.
    
    I'm open to changing the style. For instance:
    - having a space after if/for/while,
    - always putting method return types on their own line.
    - Putting the { on the same line.

 .clang-format |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)
---
diff --git a/.clang-format b/.clang-format
new file mode 100644
index 0000000..0f1ad0d
--- /dev/null
+++ b/.clang-format
@@ -0,0 +1,7 @@
+BasedOnStyle: Mozilla
+AlignAfterOpenBracket: false
+Standard: Cpp11
+BreakBeforeBraces: Allman
+SpaceBeforeParens: Never
+
+