Add clang-format file

Also run it across the whole tree to get everything using the One True Style.
We don't yet run this in an automated fashion as it's a little slow, but
there is a snippet to do so in makeall.sh.

LibGUI/GMessageBox.h

@@ -4,7 +4,8 @@
 
 class GMessageBox : public GDialog {
 public:
-    enum class Type {
+    enum class Type
+    {
         None,
         Information,
         Warning,