clang-format syntax

[Murray Cumming <murrayc murrayc com>]

I'd quite like to run clang-format on all our source code. I'd even
like to optionally run it over our generated source code at build time.

I've added a clang-format syntax file for people to try out:
https://git.gnome.org/browse/gtkmm/commit/?id=66f1468b7548e22dd574f170c
5930c9e61724200

At this point we might want to agree on a code style, if we can,
without bikeshedding, please. If you have ever provided a patch or
commit and you have an opinion, please give it briefly.


-- 
Murray Cumming
murrayc murrayc com
www.murrayc.com