Make stat() work on device files again.

FileDescriptor will now keep a pointer to the original inode even after
opening it resolves to a character device.

Fixed up /bin/ls to display major and minor device numbers instead of size
for device files.

Kernel/VirtualFileSystem.h

@@ -24,6 +24,7 @@
 #define O_NOFOLLOW 00400000
 #define O_CLOEXEC 02000000
 #define O_NOFOLLOW_NOERROR 0x4000000
+#define O_DONT_OPEN_DEVICE 0x8000000
 
 class CharacterDevice;
 class FileDescriptor;