Meta: Add a script check the presence of "#pragma once" in header files

.. and make travis run it.

I renamed check-license-headers.sh to check-style.sh and expanded it so
that it now also checks for the presence of "#pragma once" in .h files.

It also checks the presence of a (single) blank line above and below the
"#pragma once" line.

I also added "#pragma once" to all the files that need it: even the ones
we are not check.
I also added/removed blank lines in order to make the script not fail.

I also ran clang-format on the files I modified.

Kernel/Devices/PATAChannel.h

@@ -34,17 +34,18 @@
 // More information about the ATA spec for PATA can be found here:
 //      ftp://ftp.seagate.com/acrobat/reference/111-1c.pdf
 //
+
 #pragma once
 
 #include <AK/OwnPtr.h>
 #include <AK/RefPtr.h>
+#include <Kernel/IO.h>
 #include <Kernel/Lock.h>
 #include <Kernel/PCI/Access.h>
 #include <Kernel/PCI/Device.h>
+#include <Kernel/PhysicalAddress.h>
 #include <Kernel/VM/PhysicalPage.h>
 #include <Kernel/WaitQueue.h>
-#include <Kernel/IO.h>
-#include <Kernel/PhysicalAddress.h>
 
 namespace Kernel {
 

Kernel/Devices/PATADiskDevice.h

@@ -27,7 +27,7 @@
 //
 // A Disk Device Connected to a PATA Channel
 //
-//
+
 #pragma once
 
 #include <Kernel/Devices/BlockDevice.h>

Kernel/Devices/SerialDevice.h

@@ -24,6 +24,8 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#pragma once
+
 #include <Kernel/Devices/CharacterDevice.h>
 
 namespace Kernel {

Kernel/FileSystem/ext2_types.h

@@ -24,6 +24,8 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#pragma once
+
 /* 
  * If linux/types.h is already been included, assume it has defined
  * everything we need.  (cross fingers)  Other header files may have 

Kernel/PCI/IOAccess.h

@@ -25,6 +25,7 @@
  */
 
 #pragma once
+
 #include <Kernel/PCI/Access.h>
 
 namespace Kernel {

Kernel/PCI/MMIOAccess.h

@@ -25,6 +25,7 @@
  */
 
 #pragma once
+
 #include <AK/HashMap.h>
 #include <AK/OwnPtr.h>
 #include <AK/Types.h>

Kernel/Ptrace.h

@@ -25,6 +25,7 @@
  */
 
 #pragma once
+
 #include <Kernel/KResult.h>
 #include <Kernel/Process.h>
 #include <Kernel/Syscall.h>