Add missing copyright headers and fix formatting

Using `misc/scripts/fix_headers.py` on all Godot files.
Some missing header guards were added, and the header inclusion order
was fixed in the Bullet module.

scene/gui/check_button.h

@@ -27,6 +27,7 @@
 /* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
 /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
 /*************************************************************************/
+
 #ifndef CHECK_BUTTON_H
 #define CHECK_BUTTON_H