libfdisk: add fdisk_locate_disklabel()

The function returns offset and size of disklabel elements.

Signed-off-by: Karel Zak <kzak@redhat.com>
libfdisk: (gpt) support for disklabel dump

Signed-off-by: Karel Zak <kzak@redhat.com>
fdisk: rewrite dump first sector add dump disklabel command

Expert command (m for help): D

PMBR: offset = 0, size = 512 bytes.
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
*
000001c0  01 00 ee fe ff ff 01 00  00 00 ff 9f 0f 00 00 00
000001d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
*
000001f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 55 aa

GPT Header: offset = 512, size = 512 bytes.
00000200  45 46 49 20 50 41 52 54  00 00 01 00 00 02 00 00
00000210  ae 36 81 28 00 00 00 00  01 00 00 00 00 00 00 00
00000220  ff 9f 0f 00 00 00 00 00  00 08 00 00 00 00 00 00
00000230  de 9f 0f 00 00 00 00 00  e0 9d d8 d5 d6 da 1a 44
00000240  98 57 e4 11 64 88 ce 3b  02 00 00 00 00 00 00 00
00000250  80 00 00 00 80 00 00 00  4b c7 c9 54 00 00 00 00
00000260  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
*

GPT Entries: offset = 1024, size = 16384 bytes.
00000400  af 3d c6 0f 83 84 72 47  8e 79 3d 69 d8 47 7d e4
00000410  bc ae 48 5e 22 e5 ca 4c  aa 98 14 6d c9 1d 72 f4
00000420  00 08 00 00 00 00 00 00  de 9f 0f 00 00 00 00 00
00000430  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
*

Signed-off-by: Karel Zak <kzak@redhat.com>