hddmenu: Support ext4 for formating disk

- Support ext4 for formating disk (require /sbin/mkfs.ext4)
- Support ext4 for check disk (require /sbin/fsck.ext4 or /sbin/e2fsck)
- Display disk format in menu (require /sbin/blkid)
- 'ext4' and 'display disk format' disabled when required files not present

src/gui/hdd_menu.h

@@ -28,6 +28,13 @@
 
 using namespace std;
 
+enum {
+	fs_ext3,
+	fs_ext4,
+
+	fs_max
+};
+
 class CHDDDestExec : public CMenuTarget
 {
 public: