Kernel: Move File.{cpp,h} into FileSystem/

Also tweak the kernel's Makefile to use -nostdinc and -nostdinc++.
This prevents us from picking up random headers from ../Root, which may
include older versions of kernel headers.

Since we still need <initializer_list> for Vector, we specifically include
the necessary GCC path. This is a bit hackish but it works for now.

Kernel/Devices/Device.h

@@ -9,7 +9,7 @@
 // There are two main subclasses:
 //   - BlockDevice (random access)
 //   - CharacterDevice (sequential)
-#include <Kernel/File.h>
+#include <Kernel/FileSystem/File.h>
 #include <Kernel/UnixTypes.h>
 
 class Device : public File {

Kernel/Devices/IDEDiskDevice.cpp

@@ -1,7 +1,7 @@
 #include <Kernel/Devices/IDEDiskDevice.h>
 #include <Kernel/FileSystem/ProcFS.h>
 #include <Kernel/IO.h>
-#include <Kernel/PIC.h>
+#include <Kernel/Arch/i386/PIC.h>
 #include <Kernel/Process.h>
 #include <Kernel/StdLib.h>
 #include <Kernel/VM/MemoryManager.h>

Kernel/Devices/PCSpeaker.cpp

@@ -1,7 +1,7 @@
 #include <Kernel/Arch/i386/CPU.h>
+#include <Kernel/Arch/i386/PIT.h>
 #include <Kernel/Devices/PCSpeaker.h>
 #include <Kernel/IO.h>
-#include <Kernel/i8253.h>
 
 void PCSpeaker::tone_on(int frequency)
 {