PartitionTable: Initial GPT Support, Adding Block Limit

Also added a script to handle creation of GPT partitioned disk (with
GRUB config file). Block limit will be used to disallow potential access
to other partitions.

Kernel/Devices/GPTPartitionTable.h

@@ -0,0 +1,60 @@
+#pragma once
+
+#include <AK/RefPtr.h>
+#include <AK/Vector.h>
+#include <Kernel/Devices/DiskDevice.h>
+#include <Kernel/Devices/DiskPartition.h>
+
+#define GPT_SIGNATURE2 0x54524150
+#define GPT_SIGNATURE 0x20494645
+#define BytesPerSector 512
+
+struct GPTPartitionEntry {
+    u32 partition_guid[4];
+    u32 unique_guid[4];
+
+    u32 first_lba[2];
+    u32 last_lba[2];
+
+    u64 attributes;
+    u8 partition_name[72];
+} __attribute__((packed));
+
+struct GPTPartitionHeader {
+    u32 sig[2];
+    u32 revision;
+    u32 header_size;
+    u32 crc32_header;
+    u32 reserved;
+    u64 current_lba;
+    u64 backup_lba;
+
+    u64 first_usable_lba;
+    u64 last_usable_lba;
+
+    u64 disk_guid1[2];
+
+    u64 partition_array_start_lba;
+
+    u32 entries_count;
+    u32 partition_entry_size;
+    u32 crc32_entries_array;
+} __attribute__((packed));
+
+class GPTPartitionTable {
+
+public:
+    explicit GPTPartitionTable(DiskDevice&);
+    ~GPTPartitionTable();
+
+    bool initialize();
+    RefPtr<DiskPartition> partition(unsigned index);
+
+private:
+    NonnullRefPtr<DiskDevice> m_device;
+
+    ByteBuffer read_header() const;
+    const GPTPartitionHeader& header() const;
+
+    u8 m_cached_header[512];
+};